From 1406c22a646a2e10255b039d3fbc6a042476b8a1 Mon Sep 17 00:00:00 2001
From: Raymond Feng <raymond@strongloop.com>
Date: Sun, 15 Jun 2014 15:53:58 -0700
Subject: [PATCH 1/8] Refactor relation into classes

---
 lib/relation-definition.js | 641 +++++++++++++++++++++++++++++++++++++
 lib/relations.js           | 384 +---------------------
 test/loopback-dl.test.js   |  18 +-
 3 files changed, 668 insertions(+), 375 deletions(-)
 create mode 100644 lib/relation-definition.js

diff --git a/lib/relation-definition.js b/lib/relation-definition.js
new file mode 100644
index 00000000..b3dfe835
--- /dev/null
+++ b/lib/relation-definition.js
@@ -0,0 +1,641 @@
+/*!
+ * Dependencies
+ */
+var assert = require('assert');
+var util = require('util');
+var i8n = require('inflection');
+var defineScope = require('./scope.js').defineScope;
+var ModelBaseClass = require('./model.js');
+
+exports.Relation = Relation;
+exports.RelationDefinition = RelationDefinition;
+
+var RelationTypes = {
+  belongsTo: 'belongsTo',
+  hasMany: 'hasMany',
+  hasOne: 'hasOne',
+  hasAndBelongsToMany: 'hasAndBelongsToMany'
+};
+
+exports.RelationTypes = RelationTypes;
+exports.HasMany = HasMany;
+exports.HasManyThrough = HasManyThrough;
+exports.HasOne = HasOne;
+exports.HasAndBelongsToMany = HasAndBelongsToMany;
+exports.BelongsTo = BelongsTo;
+
+var RelationClasses = {
+  belongsTo: BelongsTo,
+  hasMany: HasMany,
+  hasManyThrough: HasManyThrough,
+  hasOne: HasOne,
+  hasAndBelongsToMany: HasAndBelongsToMany
+};
+
+function normalizeType(type) {
+  if (!type) {
+    return type;
+  }
+  var t1 = type.toLowerCase();
+  for (var t2 in RelationTypes) {
+    if (t2.toLowerCase() === t1) {
+      return t2;
+    }
+  }
+  return null;
+}
+
+/**
+ * Relation definition class.  Use to define relationships between models.
+ * @param {Object} definition
+ * @class RelationDefinition
+ */
+function RelationDefinition(definition) {
+  if (!(this instanceof RelationDefinition)) {
+    return new RelationDefinition(definition);
+  }
+  definition = definition || {};
+  this.name = definition.name;
+  assert(this.name, 'Relation name is missing');
+  this.type = normalizeType(definition.type);
+  assert(this.type, 'Invalid relation type: ' + definition.type);
+  this.modelFrom = definition.modelFrom;
+  assert(this.modelFrom);
+  this.keyFrom = definition.keyFrom;
+  this.modelTo = definition.modelTo;
+  assert(this.modelTo);
+  this.keyTo = definition.keyTo;
+  this.modelThrough = definition.modelThrough;
+  this.keyThrough = definition.keyThrough;
+  this.multiple = (this.type !== 'belongsTo' && this.type !== 'hasOne');
+}
+
+RelationDefinition.prototype.toJSON = function () {
+  var json = {
+    name: this.name,
+    type: this.type,
+    modelFrom: this.modelFrom.modelName,
+    keyFrom: this.keyFrom,
+    modelTo: this.modelTo.modelName,
+    keyTo: this.keyTo,
+    multiple: this.multiple
+  };
+  if (this.modelThrough) {
+    json.modelThrough = this.modelThrough.modelName;
+    json.keyThrough = this.keyThrough;
+  }
+  return json;
+};
+
+/**
+ * A relation attaching to a given model instance
+ * @param {RelationDefinition|Object} definition
+ * @param {Object} modelInstance
+ * @returns {Relation}
+ * @constructor
+ * @class Relation
+ */
+function Relation(definition, modelInstance) {
+  if (!(this instanceof Relation)) {
+    return new Relation(definition, modelInstance);
+  }
+  if (!(definition instanceof RelationDefinition)) {
+    definition = new RelationDefinition(definition);
+  }
+  this.definition = definition;
+  this.modelInstance = modelInstance;
+}
+
+/**
+ * HasMany subclass
+ * @param {RelationDefinition|Object} definition
+ * @param {Object} modelInstance
+ * @returns {HasMany}
+ * @constructor
+ * @class HasMany
+ */
+function HasMany(definition, modelInstance) {
+  if (!(this instanceof HasMany)) {
+    return new HasMany(definition, modelInstance);
+  }
+  assert(definition.type === RelationTypes.hasMany);
+  Relation.apply(this, arguments);
+}
+
+util.inherits(HasMany, Relation);
+
+/**
+ * HasManyThrough subclass
+ * @param {RelationDefinition|Object} definition
+ * @param {Object} modelInstance
+ * @returns {HasManyThrough}
+ * @constructor
+ * @class HasManyThrough
+ */
+function HasManyThrough(definition, modelInstance) {
+  if (!(this instanceof HasManyThrough)) {
+    return new HasManyThrough(definition, modelInstance);
+  }
+  assert(definition.type === RelationTypes.hasMany);
+  assert(definition.modelThrough);
+  HasMany.apply(this, arguments);
+}
+
+util.inherits(HasManyThrough, HasMany);
+
+/**
+ * BelongsTo subclass
+ * @param {RelationDefinition|Object} definition
+ * @param {Object} modelInstance
+ * @returns {BelongsTo}
+ * @constructor
+ * @class BelongsTo
+ */
+function BelongsTo(definition, modelInstance) {
+  if (!(this instanceof BelongsTo)) {
+    return new BelongsTo(definition, modelInstance);
+  }
+  assert(definition.type === RelationTypes.belongsTo);
+  Relation.apply(this, arguments);
+}
+
+util.inherits(BelongsTo, Relation);
+
+/**
+ * HasAndBelongsToMany subclass
+ * @param {RelationDefinition|Object} definition
+ * @param {Object} modelInstance
+ * @returns {HasAndBelongsToMany}
+ * @constructor
+ * @class HasAndBelongsToMany
+ */
+function HasAndBelongsToMany(definition, modelInstance) {
+  if (!(this instanceof HasAndBelongsToMany)) {
+    return new HasAndBelongsToMany(definition, modelInstance);
+  }
+  assert(definition.type === RelationTypes.hasAndBelongsToMany);
+  Relation.apply(this, arguments);
+}
+
+util.inherits(HasAndBelongsToMany, Relation);
+
+/**
+ * HasOne subclass
+ * @param {RelationDefinition|Object} definition
+ * @param {Object} modelInstance
+ * @returns {HasOne}
+ * @constructor
+ * @class HasOne
+ */
+function HasOne(definition, modelInstance) {
+  if (!(this instanceof HasOne)) {
+    return new HasOne(definition, modelInstance);
+  }
+  assert(definition.type === RelationTypes.hasOne);
+  Relation.apply(this, arguments);
+}
+
+util.inherits(HasOne, Relation);
+
+
+/*!
+ * Find the relation by foreign key
+ * @param {*} foreignKey The foreign key
+ * @returns {Object} The relation object
+ */
+function findBelongsTo(model, foreignKey) {
+  var relations = model.relations;
+  var keys = Object.keys(relations);
+  for (var k = 0; k < keys.length; k++) {
+    var rel = relations[keys[k]];
+    if (rel.type === RelationTypes.belongsTo &&
+      rel.keyFrom === foreignKey) {
+      return keys[k];
+    }
+  }
+  return null;
+}
+
+/*!
+ * Look up a model by name from the list of given models
+ * @param {Object} models Models keyed by name
+ * @param {String} modelName The model name
+ * @returns {*} The matching model class
+ */
+function lookupModel(models, modelName) {
+  if(models[modelName]) {
+    return models[modelName];
+  }
+  var lookupClassName = modelName.toLowerCase();
+  for (var name in models) {
+    if (name.toLowerCase() === lookupClassName) {
+      return models[name];
+    }
+  }
+}
+
+/**
+ * Define a "one to many" relationship by specifying the model name
+ * 
+ * Examples:
+ * ```
+ * User.hasMany(Post, {as: 'posts', foreignKey: 'authorId'});
+ * ```
+ * 
+ * ```
+ * Book.hasMany(Chapter);
+ * ```
+ * Or, equivalently:
+ * ```
+ * Book.hasMany('chapters', {model: Chapter});
+ * ```
+ * @param {Model} modelFrom Source model class
+ * @param {Object|String} modelTo Model object (or String name of model) to which you are creating the relationship.
+ * @options {Object} params Configuration parameters; see below.
+ * @property {String} as Name of the property in the referring model that corresponds to the foreign key field in the related model.
+ * @property {String} foreignKey Property name of foreign key field.
+ * @property {Object} model Model object
+ */
+RelationDefinition.hasMany = function hasMany(modelFrom, modelTo, params) {
+  var thisClassName = modelFrom.modelName;
+  params = params || {};
+  if (typeof modelTo === 'string') {
+    params.as = modelTo;
+    if (params.model) {
+      modelTo = params.model;
+    } else {
+      var modelToName = i8n.singularize(modelTo).toLowerCase();
+      modelTo = lookupModel(modelFrom.dataSource.modelBuilder.models, modelToName);
+    }
+  }
+  var relationName = params.as || i8n.camelize(modelTo.pluralModelName, true);
+  var fk = params.foreignKey || i8n.camelize(thisClassName + '_id', true);
+
+  var idName = modelFrom.dataSource.idName(modelFrom.modelName) || 'id';
+
+  var definition = new RelationDefinition({
+    name: relationName,
+    type: RelationTypes.hasMany,
+    modelFrom: modelFrom,
+    keyFrom: idName,
+    keyTo: fk,
+    modelTo: modelTo,
+    multiple: true
+  });
+
+  if (params.through) {
+    definition.modelThrough = params.through;
+    var keyThrough = definition.throughKey || i8n.camelize(modelTo.modelName + '_id', true);
+    definition.keyThrough = keyThrough;
+  }
+
+  modelFrom.relations[relationName] = definition;
+
+  if (!params.through) {
+    // obviously, modelTo should have attribute called `fk`
+    modelTo.dataSource.defineForeignKey(modelTo.modelName, fk, this.modelName);
+  }
+
+  var scopeMethods = {
+    findById: scopeMethod(definition, 'findById'),
+    destroy: scopeMethod(definition, 'destroyById')
+  }
+
+  if(definition.modelThrough) {
+    scopeMethods.create = scopeMethod(definition, 'create');
+    scopeMethods.add = scopeMethod(definition, 'add');
+    scopeMethods.remove = scopeMethod(definition, 'remove');
+  }
+
+  // Mix the property and scoped methods into the prototype class
+  defineScope(modelFrom.prototype, params.through || modelTo, relationName, function () {
+    var filter = {};
+    filter.where = {};
+    filter.where[fk] = this[idName];
+    if (params.through) {
+      filter.collect = i8n.camelize(modelTo.modelName, true);
+      filter.include = filter.collect;
+    }
+    return filter;
+  }, scopeMethods);
+
+};
+
+function scopeMethod(definition, methodName) {
+  var method = function () {
+    var relationClass = RelationClasses[definition.type];
+    if (definition.type === RelationTypes.hasMany && definition.modelThrough) {
+      relationClass = RelationClasses.hasManyThrough;
+    }
+    var relation = new relationClass(definition, this);
+    return relation[methodName].apply(relation, arguments);
+  };
+  return method;
+}
+
+HasMany.prototype.findById = function (id, cb) {
+  var modelTo = this.definition.modelTo;
+  var fk = this.definition.keyTo;
+  var pk = this.definition.keyFrom;
+  var modelInstance = this.modelInstance;
+  modelTo.findById(id, function (err, inst) {
+    if (err) {
+      return cb(err);
+    }
+    if (!inst) {
+      return cb(new Error('Not found'));
+    }
+    // Check if the foreign key matches the primary key
+    if (inst[fk] && inst[fk].toString() === modelInstance[pk].toString()) {
+      cb(null, inst);
+    } else {
+      cb(new Error('Permission denied: foreign key does not match the primary key'));
+    }
+  });
+};
+
+HasMany.prototype.destroyById = function (id, cb) {
+  var modelTo = this.definition.modelTo;
+  var fk = this.definition.keyTo;
+  var pk = this.definition.keyFrom;
+  var modelInstance = this.modelInstance;
+  modelTo.findById(id, function (err, inst) {
+    if (err) {
+      return cb(err);
+    }
+    if (!inst) {
+      return cb(new Error('Not found'));
+    }
+    // Check if the foreign key matches the primary key
+    if (inst[fk] && inst[fk].toString() === modelInstance[pk].toString()) {
+      inst.destroy(cb);
+    } else {
+      cb(new Error('Permission denied: foreign key does not match the primary key'));
+    }
+  });
+};
+
+// Create an instance of the target model and connect it to the instance of
+// the source model by creating an instance of the through model
+HasManyThrough.prototype.create = function create(data, done) {
+  var modelTo = this.definition.modelTo;
+  var modelThrough = this.definition.modelThrough;
+  var fk = this.definition.keyTo;
+  var fk2 = this.definition.keyThrough;
+
+  if (typeof data === 'function' && !done) {
+    done = data;
+    data = {};
+  }
+
+  var self = this.modelInstance;
+  // First create the target model
+  modelTo.create(data, function (err, ac) {
+    if (err) {
+      return done && done(err, ac);
+    }
+    var d = {};
+    d[findBelongsTo(modelThrough, fk)] = self;
+    d[findBelongsTo(modelThrough, fk2)] = ac;
+    // Then create the through model
+    modelThrough.create(d, function (e) {
+      if (e) {
+        // Undo creation of the target model
+        ac.destroy(function () {
+          done && done(e);
+        });
+      } else {
+        done && done(err, ac);
+      }
+    });
+  });
+};
+
+/**
+ * Add the target model instance to the 'hasMany' relation
+ * @param {Object|ID} acInst The actual instance or id value
+ */
+HasManyThrough.prototype.add = function (acInst, done) {
+  var modelThrough = this.definition.modelThrough;
+  var fk = this.definition.keyTo;
+  var fk2 = this.definition.keyThrough;
+  var pk = this.definition.keyFrom;
+
+  var data = {};
+  var query = {};
+  query[fk] = this[pk];
+  data[findBelongsTo(modelThrough, fk)] = this.modelInstance;
+  query[fk2] = acInst[pk] || acInst;
+  data[findBelongsTo(modelThrough, fk2)] = acInst;
+  // Create an instance of the through model
+  modelThrough.findOrCreate({where: query}, data, done);
+};
+
+/**
+ * Remove the target model instance from the 'hasMany' relation
+ * @param {Object|ID) acInst The actual instance or id value
+ */
+HasManyThrough.prototype.remove = function (acInst, done) {
+  var modelThrough = this.definition.modelThrough;
+  var fk2 = this.definition.keyThrough;
+  var pk = this.definition.keyFrom;
+
+  var q = {};
+  q[fk2] = acInst[pk] || acInst;
+  modelThrough.deleteAll(q, done );
+};
+
+
+/**
+ * Declare "belongsTo" relation that sets up a one-to-one connection with
+ * another model, such that each instance of the declaring model "belongs to"
+ * one instance of the other model.
+ *
+ * For example, if an application includes users and posts, and each post can
+ * be written by exactly one user. The following code specifies that `Post` has
+ * a reference called `author` to the `User` model via the `userId` property of
+ * `Post` as the foreign key.
+ * ```
+ * Post.belongsTo(User, {as: 'author', foreignKey: 'userId'});
+ * ```
+ *
+ * This optional parameter default value is false, so the related object will
+ * be loaded from cache if available.
+ * 
+ * @param {Class|String} modelTo Model object (or String name of model) to
+ * which you are creating the relationship.
+ * @options {Object} params Configuration parameters; see below.
+ * @property {String} as Name of the property in the referring model that
+ * corresponds to the foreign key field in the related model.
+ * @property {String} foreignKey Name of foreign key property.
+ * 
+ */
+RelationDefinition.belongsTo = function (modelFrom, modelTo, params) {
+  params = params || {};
+  if ('string' === typeof modelTo) {
+    params.as = modelTo;
+    if (params.model) {
+      modelTo = params.model;
+    } else {
+      var modelToName = modelTo.toLowerCase();
+      modelTo = lookupModel(modelFrom.dataSource.modelBuilder.models, modelToName);
+    }
+  }
+
+  var idName = modelFrom.dataSource.idName(modelTo.modelName) || 'id';
+  var relationName = params.as || i8n.camelize(modelTo.modelName, true);
+  var fk = params.foreignKey || relationName + 'Id';
+
+  var relationDef = modelFrom.relations[relationName] = new RelationDefinition({
+    name: relationName,
+    type: RelationTypes.belongsTo,
+    modelFrom: modelFrom,
+    keyFrom: fk,
+    keyTo: idName,
+    modelTo: modelTo
+  });
+
+  modelFrom.dataSource.defineForeignKey(modelFrom.modelName, fk, modelTo.modelName);
+
+  // Define a property for the scope so that we have 'this' for the scoped methods
+  Object.defineProperty(modelFrom.prototype, relationName, {
+    enumerable: true,
+    configurable: true,
+    get: function() {
+      var relation = new BelongsTo(relationDef, this);
+      var relationMethod = relation.related.bind(relation)
+      relationMethod.create = relation.create.bind(relation);
+      relationMethod.build = relation.build.bind(relation);
+      return relationMethod;
+    }
+  });
+};
+
+BelongsTo.prototype.create = function(targetModelData, cb) {
+  var modelTo = this.definition.modelTo;
+  var fk = this.definition.keyTo;
+  var pk = this.definition.keyFrom;
+  var modelInstance = this.modelInstance;
+
+  modelTo.create(targetModelData, function(err, targetModel) {
+    if(!err) {
+      modelInstance[fk] = targetModel[pk];
+      cb && cb(err, targetModel);
+    } else {
+      cb && cb(err);
+    }
+  });
+};
+
+BelongsTo.prototype.build = function(targetModelData) {
+  var modelTo = this.definition.modelTo;
+  return new modelTo(targetModelData);
+};
+
+/**
+ * Define the method for the belongsTo relation itself
+ * It will support one of the following styles:
+ * - order.customer(refresh, callback): Load the target model instance asynchronously
+ * - order.customer(customer): Synchronous setter of the target model instance
+ * - order.customer(): Synchronous getter of the target model instance
+ *
+ * @param refresh
+ * @param params
+ * @returns {*}
+ */
+BelongsTo.prototype.related = function (refresh, params) {
+  var modelTo = this.definition.modelTo;
+  var pk = this.definition.keyTo;
+  var fk = this.definition.keyFrom;
+  var modelInstance = this.modelInstance;
+  var relationName = this.definition.name;
+
+  if (arguments.length === 1) {
+    params = refresh;
+    refresh = false;
+  } else if (arguments.length > 2) {
+    throw new Error('Method can\'t be called with more than two arguments');
+  }
+
+  var cachedValue;
+  if (!refresh && modelInstance.__cachedRelations
+    && (modelInstance.__cachedRelations[relationName] !== undefined)) {
+    cachedValue = modelInstance.__cachedRelations[relationName];
+  }
+  if (params instanceof ModelBaseClass) { // acts as setter
+    modelInstance[fk] = params[pk];
+    modelInstance.__cachedRelations[relationName] = params;
+  } else if (typeof params === 'function') { // acts as async getter
+    var cb = params;
+    if (cachedValue === undefined) {
+      modelTo.findById(modelInstance[fk], function (err, inst) {
+        if (err) {
+          return cb(err);
+        }
+        if (!inst) {
+          return cb(null, null);
+        }
+        // Check if the foreign key matches the primary key
+        if (inst[pk] === modelInstance[fk]) {
+          cb(null, inst);
+        } else {
+          cb(new Error('Permission denied'));
+        }
+      });
+      return modelInstance[fk];
+    } else {
+      cb(null, cachedValue);
+      return cachedValue;
+    }
+  } else if (params === undefined) { // acts as sync getter
+    return modelInstance[fk];
+  } else { // setter
+    modelInstance[fk] = params;
+    delete modelInstance.__cachedRelations[relationName];
+  }
+};
+
+/**
+ * A hasAndBelongsToMany relation creates a direct many-to-many connection with another model, with no intervening model.
+ * For example, if your application includes users and groups, with each group having many users and each user appearing
+ * in many groups, you could declare the models this way:
+ * ```
+ *  User.hasAndBelongsToMany('groups', {model: Group, foreignKey: 'groupId'});
+ * ```
+ * 
+ * @param {String|Object} modelTo Model object (or String name of model) to which you are creating the relationship.
+ * the relation
+ * @options {Object} params Configuration parameters; see below.
+ * @property {String} as Name of the property in the referring model that corresponds to the foreign key field in the related model.
+ * @property {String} foreignKey Property name of foreign key field.
+ * @property {Object} model Model object
+ */
+RelationDefinition.hasAndBelongsToMany = function hasAndBelongsToMany(modelFrom, modelTo, params) {
+  params = params || {};
+  var models = modelFrom.dataSource.modelBuilder.models;
+
+  if ('string' === typeof modelTo) {
+    params.as = modelTo;
+    if (params.model) {
+      modelTo = params.model;
+    } else {
+      modelTo = lookupModel(models, i8n.singularize(modelTo)) ||
+        modelTo;
+    }
+    if (typeof modelTo === 'string') {
+      throw new Error('Could not find "' + modelTo + '" relation for ' + modelFrom.modelName);
+    }
+  }
+
+  if (!params.through) {
+    var name1 = modelFrom.modelName + modelTo.modelName;
+    var name2 = modelTo.modelName + modelFrom.modelName;
+    params.through = lookupModel(models, name1) || lookupModel(models, name2) ||
+      modelFrom.dataSource.define(name1);
+  }
+  params.through.belongsTo(modelFrom);
+  params.through.belongsTo(modelTo);
+
+  this.hasMany(modelFrom, modelTo, {as: params.as, through: params.through});
+
+};
diff --git a/lib/relations.js b/lib/relations.js
index c07b87d2..8b740359 100644
--- a/lib/relations.js
+++ b/lib/relations.js
@@ -1,49 +1,17 @@
 /*!
  * Dependencies
  */
-var i8n = require('inflection');
-var defineScope = require('./scope.js').defineScope;
-var ModelBaseClass = require('./model.js');
+var relation = require('./relation-definition');
+var RelationDefinition = relation.RelationDefinition;
 
-module.exports = Relation;
+module.exports = RelationMixin;
 
 /**
- * Relations class.  Use to define relationships between models.
+ * RelationMixin class.  Use to define relationships between models.
  *
- * @class Relation
+ * @class RelationMixin
  */
-function Relation() {
-}
-
-/**
- * Find the relation by foreign key
- * @param {*} foreignKey The foreign key
- * @returns {Object} The relation object
- */
-Relation.relationNameFor = function relationNameFor(foreignKey) {
-  for (var rel in this.relations) {
-    if (this.relations[rel].type === 'belongsTo' && this.relations[rel].keyFrom === foreignKey) {
-      return rel;
-    }
-  }
-};
-
-/*!
- * Look up a model by name from the list of given models
- * @param {Object} models Models keyed by name
- * @param {String} modelName The model name
- * @returns {*} The matching model class
- */
-function lookupModel(models, modelName) {
-  if(models[modelName]) {
-    return models[modelName];
-  }
-  var lookupClassName = modelName.toLowerCase();
-  for (var name in models) {
-    if (name.toLowerCase() === lookupClassName) {
-      return models[name];
-    }
-  }
+function RelationMixin() {
 }
 
 /**
@@ -90,173 +58,14 @@ function lookupModel(models, modelName) {
  *   });
  * });
  *```
- * @param {Object|String} anotherClass Model object (or String name of model) to which you are creating the relationship.
+ * @param {Object|String} modelTo Model object (or String name of model) to which you are creating the relationship.
  * @options {Object} parameters Configuration parameters; see below. 
  * @property {String} as Name of the property in the referring model that corresponds to the foreign key field in the related model.
  * @property {String} foreignKey Property name of foreign key field.
  * @property {Object} model Model object
  */
-Relation.hasMany = function hasMany(anotherClass, params) {
-  var thisClassName = this.modelName;
-  params = params || {};
-  if (typeof anotherClass === 'string') {
-    params.as = anotherClass;
-    if (params.model) {
-      anotherClass = params.model;
-    } else {
-      var anotherClassName = i8n.singularize(anotherClass).toLowerCase();
-      anotherClass = lookupModel(this.dataSource.modelBuilder.models, anotherClassName);
-    }
-  }
-  var methodName = params.as || i8n.camelize(anotherClass.pluralModelName, true);
-  var fk = params.foreignKey || i8n.camelize(thisClassName + '_id', true);
-
-  var idName = this.dataSource.idName(this.modelName) || 'id';
-
-  this.relations[methodName] = {
-    type: 'hasMany',
-    keyFrom: idName,
-    keyTo: fk,
-    modelTo: anotherClass,
-    multiple: true
-  };
-
-  if (params.through) {
-    this.relations[methodName].modelThrough = params.through;
-  }
-  // each instance of this class should have method named
-  // pluralize(anotherClass.modelName)
-  // which is actually just anotherClass.find({where: {thisModelNameId: this[idName]}}, cb);
-  var scopeMethods = {
-    findById: findById,
-    destroy: destroyById
-  };
-  if (params.through) {
-    var fk2 = i8n.camelize(anotherClass.modelName + '_id', true);
-
-    // Create an instance of the target model and connect it to the instance of
-    // the source model by creating an instance of the through model
-    scopeMethods.create = function create(data, done) {
-      if (typeof data !== 'object') {
-        done = data;
-        data = {};
-      }
-      if ('function' !== typeof done) {
-        done = function () {
-        };
-      }
-      var self = this;
-      // First create the target model
-      anotherClass.create(data, function (err, ac) {
-        if (err) return done(err, ac);
-        var d = {};
-        d[params.through.relationNameFor(fk)] = self;
-        d[params.through.relationNameFor(fk2)] = ac;
-        // Then create the through model
-        params.through.create(d, function (e) {
-          if (e) {
-            // Undo creation of the target model
-            ac.destroy(function () {
-              done(e);
-            });
-          } else {
-            done(err, ac);
-          }
-        });
-      });
-    };
-
-    /*!
-     * Add the target model instance to the 'hasMany' relation
-     * @param {Object|ID} acInst The actual instance or id value
-     */
-    scopeMethods.add = function (acInst, done) {
-      var data = {};
-      var query = {};
-      query[fk] = this[idName];
-      data[params.through.relationNameFor(fk)] = this;
-      query[fk2] = acInst[idName] || acInst;
-      data[params.through.relationNameFor(fk2)] = acInst;
-      // Create an instance of the through model
-      params.through.findOrCreate({where: query}, data, done);
-    };
-
-    /*!
-     * Remove the target model instance from the 'hasMany' relation
-     * @param {Object|ID) acInst The actual instance or id value
-     */
-    scopeMethods.remove = function (acInst, done) {
-      var q = {};
-      q[fk2] = acInst[idName] || acInst;
-      params.through.findOne({where: q}, function (err, d) {
-        if (err) {
-          return done(err);
-        }
-        if (!d) {
-          return done();
-        }
-        d.destroy(done);
-      });
-    };
-
-    // No destroy method will be injected
-    delete scopeMethods.destroy;
-  }
-
-  // Mix the property and scoped methods into the prototype class
-  defineScope(this.prototype, params.through || anotherClass, methodName, function () {
-    var filter = {};
-    filter.where = {};
-    filter.where[fk] = this[idName];
-    if (params.through) {
-      filter.collect = i8n.camelize(anotherClass.modelName, true);
-      filter.include = filter.collect;
-    }
-    return filter;
-  }, scopeMethods);
-
-  if (!params.through) {
-    // obviously, anotherClass should have attribute called `fk`
-    anotherClass.dataSource.defineForeignKey(anotherClass.modelName, fk, this.modelName);
-  }
-
-  // Find the target model instance by id
-  function findById(id, cb) {
-    anotherClass.findById(id, function (err, inst) {
-      if (err) {
-        return cb(err);
-      }
-      if (!inst) {
-        return cb(new Error('Not found'));
-      }
-      // Check if the foreign key matches the primary key
-      if (inst[fk] && inst[fk].toString() === this[idName].toString()) {
-        cb(null, inst);
-      } else {
-        cb(new Error('Permission denied'));
-      }
-    }.bind(this));
-  }
-
-  // Destroy the target model instance by id
-  function destroyById(id, cb) {
-    var self = this;
-    anotherClass.findById(id, function (err, inst) {
-      if (err) {
-        return cb(err);
-      }
-      if (!inst) {
-        return cb(new Error('Not found'));
-      }
-      // Check if the foreign key matches the primary key
-      if (inst[fk] && inst[fk].toString() === self[idName].toString()) {
-        inst.destroy(cb);
-      } else {
-        cb(new Error('Permission denied'));
-      }
-    });
-  }
-
+RelationMixin.hasMany = function hasMany(modelTo, params) {
+  RelationDefinition.hasMany(this, modelTo, params);
 };
 
 /**
@@ -304,151 +113,14 @@ Relation.hasMany = function hasMany(anotherClass, params) {
  * ```
  * This optional parameter default value is false, so the related object will be loaded from cache if available.
  * 
- * @param {Class|String} anotherClass Model object (or String name of model) to which you are creating the relationship.
+ * @param {Class|String} modelTo Model object (or String name of model) to which you are creating the relationship.
  * @options {Object} params Configuration parameters; see below.
  * @property {String} as Name of the property in the referring model that corresponds to the foreign key field in the related model.
  * @property {String} foreignKey Name of foreign key property.
  * 
  */
-Relation.belongsTo = function (anotherClass, params) {
-  params = params || {};
-  if ('string' === typeof anotherClass) {
-    params.as = anotherClass;
-    if (params.model) {
-      anotherClass = params.model;
-    } else {
-      var anotherClassName = anotherClass.toLowerCase();
-      anotherClass = lookupModel(this.dataSource.modelBuilder.models, anotherClassName);
-    }
-  }
-
-  var idName = this.dataSource.idName(anotherClass.modelName) || 'id';
-  var methodName = params.as || i8n.camelize(anotherClass.modelName, true);
-  var fk = params.foreignKey || methodName + 'Id';
-
-  this.relations[methodName] = {
-    type: 'belongsTo',
-    keyFrom: fk,
-    keyTo: idName,
-    modelTo: anotherClass,
-    multiple: false
-  };
-
-  this.dataSource.defineForeignKey(this.modelName, fk, anotherClass.modelName);
-  this.prototype.__finders__ = this.prototype.__finders__ || {};
-
-  // Set up a finder to find by id and make sure the foreign key of the declaring
-  // model matches the primary key of the target model
-  this.prototype.__finders__[methodName] = function (id, cb) {
-    if (id === null) {
-      cb(null, null);
-      return;
-    }
-    anotherClass.findById(id, function (err, inst) {
-      if (err) {
-        return cb(err);
-      }
-      if (!inst) {
-        return cb(null, null);
-      }
-      // Check if the foreign key matches the primary key
-      if (inst[idName] === this[fk]) {
-        cb(null, inst);
-      } else {
-        cb(new Error('Permission denied'));
-      }
-    }.bind(this));
-  };
-
-  // Define the method for the belongsTo relation itself
-  // It will support one of the following styles:
-  // - order.customer(refresh, callback): Load the target model instance asynchronously
-  // - order.customer(customer): Synchronous setter of the target model instance
-  // - order.customer(): Synchronous getter of the target model instance
-  var relationMethod = function (refresh, p) {
-    if (arguments.length === 1) {
-      p = refresh;
-      refresh = false;
-    } else if (arguments.length > 2) {
-      throw new Error('Method can\'t be called with more than two arguments');
-    }
-    var self = this;
-    var cachedValue;
-    if (!refresh && this.__cachedRelations && (this.__cachedRelations[methodName] !== undefined)) {
-      cachedValue = this.__cachedRelations[methodName];
-    }
-    if (p instanceof ModelBaseClass) { // acts as setter
-      this[fk] = p[idName];
-      this.__cachedRelations[methodName] = p;
-    } else if (typeof p === 'function') { // acts as async getter
-      if (typeof cachedValue === 'undefined') {
-        this.__finders__[methodName].apply(self, [this[fk], function (err, inst) {
-          if (!err) {
-            self.__cachedRelations[methodName] = inst;
-          }
-          p(err, inst);
-        }]);
-        return this[fk];
-      } else {
-        p(null, cachedValue);
-        return cachedValue;
-      }
-    } else if (typeof p === 'undefined') { // acts as sync getter
-      return this[fk];
-    } else { // setter
-      this[fk] = p;
-      delete this.__cachedRelations[methodName];
-    }
-  };
-
-  // Define a property for the scope so that we have 'this' for the scoped methods
-  Object.defineProperty(this.prototype, methodName, {
-    enumerable: true,
-    configurable: true,
-    get: function () {
-      var fn = function() {
-        // Call the relation method on the declaring model instance
-        return relationMethod.apply(this, arguments);
-      }
-      // Create an instance of the target model and set the foreign key of the
-      // declaring model instance to the id of the target instance
-      fn.create = function(targetModelData, cb) {
-        var self = this;
-        anotherClass.create(targetModelData, function(err, targetModel) {
-          if(!err) {
-            self[fk] = targetModel[idName];
-            cb && cb(err, targetModel);
-          } else {
-            cb && cb(err);
-          }
-        });
-      }.bind(this);
-
-      // Build an instance of the target model
-      fn.build = function(targetModelData) {
-        return new anotherClass(targetModelData);
-      }.bind(this);
-
-      fn._targetClass = anotherClass.modelName;
-
-      return fn;
-    }});
-
-  // Wrap the property into a function for remoting
-  // so that it can be accessed as /api/<model>/<id>/<belongsToRelationName>
-  // For example, /api/orders/1/customer
-  var fn = function() {
-    var f = this[methodName];
-    f.apply(this, arguments);
-  };
-
-  fn.shared = true;
-  fn.http = {verb: 'get', path: '/' + methodName};
-  fn.accepts = {arg: 'refresh', type: 'boolean', http: {source: 'query'}};
-  fn.description = 'Fetches belongsTo relation ' + methodName;
-  fn.returns = {arg: methodName, type: 'object', root: true};
-
-  this.prototype['__get__' + methodName] = fn;
+RelationMixin.belongsTo = function (modelTo, params) {
+  RelationDefinition.belongsTo(this, modelTo, params);
 };
 
 /**
@@ -475,39 +147,13 @@ Relation.belongsTo = function (anotherClass, params) {
  *  user.groups.remove(group, callback); 
  * ```
  * 
- * @param {String|Object} anotherClass Model object (or String name of model) to which you are creating the relationship.
+ * @param {String|Object} modelTo Model object (or String name of model) to which you are creating the relationship.
  * the relation
  * @options {Object} params Configuration parameters; see below.
  * @property {String} as Name of the property in the referring model that corresponds to the foreign key field in the related model.
  * @property {String} foreignKey Property name of foreign key field.
  * @property {Object} model Model object
  */
-Relation.hasAndBelongsToMany = function hasAndBelongsToMany(anotherClass, params) {
-  params = params || {};
-  var models = this.dataSource.modelBuilder.models;
-
-  if ('string' === typeof anotherClass) {
-    params.as = anotherClass;
-    if (params.model) {
-      anotherClass = params.model;
-    } else {
-      anotherClass = lookupModel(models, i8n.singularize(anotherClass).toLowerCase()) ||
-        anotherClass;
-    }
-    if (typeof anotherClass === 'string') {
-      throw new Error('Could not find "' + anotherClass + '" relation for ' + this.modelName);
-    }
-  }
-
-  if (!params.through) {
-    var name1 = this.modelName + anotherClass.modelName;
-    var name2 = anotherClass.modelName + this.modelName;
-    params.through = lookupModel(models, name1) || lookupModel(models, name2) ||
-      this.dataSource.define(name1);
-  }
-  params.through.belongsTo(this);
-  params.through.belongsTo(anotherClass);
-
-  this.hasMany(anotherClass, {as: params.as, through: params.through});
-
+RelationMixin.hasAndBelongsToMany = function hasAndBelongsToMany(modelTo, params) {
+  RelationDefinition.hasAndBelongsToMany(this, modelTo, params);
 };
diff --git a/test/loopback-dl.test.js b/test/loopback-dl.test.js
index d1d2b0a8..2d840fca 100644
--- a/test/loopback-dl.test.js
+++ b/test/loopback-dl.test.js
@@ -872,27 +872,33 @@ describe('Load models with relations', function () {
     var Account = ds.define('Account', {userId: Number, type: String}, {relations: {user: {type: 'belongsTo', model: 'User'}}});
 
     assert(Post.relations['user']);
-    assert.deepEqual(Post.relations['user'], {
+    assert.deepEqual(Post.relations['user'].toJSON(), {
+      name: 'user',
       type: 'belongsTo',
+      modelFrom: 'Post',
       keyFrom: 'userId',
+      modelTo: 'User',
       keyTo: 'id',
-      modelTo: User,
       multiple: false
     });
     assert(User.relations['posts']);
-    assert.deepEqual(User.relations['posts'], {
+    assert.deepEqual(User.relations['posts'].toJSON(), {
+      name: 'posts',
       type: 'hasMany',
+      modelFrom: 'User',
       keyFrom: 'id',
+      modelTo: 'Post',
       keyTo: 'userId',
-      modelTo: Post,
       multiple: true
     });
     assert(User.relations['accounts']);
-    assert.deepEqual(User.relations['accounts'], {
+    assert.deepEqual(User.relations['accounts'].toJSON(), {
+      name: 'accounts',
       type: 'hasMany',
+      modelFrom: 'User',
       keyFrom: 'id',
+      modelTo: 'Account',
       keyTo: 'userId',
-      modelTo: Account,
       multiple: true
     });
 

From 34c1998f0406ec488edfded89b9796e77d56670e Mon Sep 17 00:00:00 2001
From: Raymond Feng <raymond@strongloop.com>
Date: Mon, 16 Jun 2014 00:36:12 -0700
Subject: [PATCH 2/8] Fix the hasMany through connection

---
 lib/relation-definition.js | 55 +++++++++++++++++++++++++-------------
 1 file changed, 36 insertions(+), 19 deletions(-)

diff --git a/lib/relation-definition.js b/lib/relation-definition.js
index b3dfe835..09849d12 100644
--- a/lib/relation-definition.js
+++ b/lib/relation-definition.js
@@ -203,14 +203,15 @@ util.inherits(HasOne, Relation);
  * @param {*} foreignKey The foreign key
  * @returns {Object} The relation object
  */
-function findBelongsTo(model, foreignKey) {
-  var relations = model.relations;
+function findBelongsTo(modelFrom, modelTo, keyTo) {
+  var relations = modelFrom.relations;
   var keys = Object.keys(relations);
   for (var k = 0; k < keys.length; k++) {
     var rel = relations[keys[k]];
     if (rel.type === RelationTypes.belongsTo &&
-      rel.keyFrom === foreignKey) {
-      return keys[k];
+      rel.modelTo === modelTo &&
+      rel.keyTo === keyTo) {
+      return rel.keyFrom;
     }
   }
   return null;
@@ -378,25 +379,30 @@ HasMany.prototype.destroyById = function (id, cb) {
 // Create an instance of the target model and connect it to the instance of
 // the source model by creating an instance of the through model
 HasManyThrough.prototype.create = function create(data, done) {
-  var modelTo = this.definition.modelTo;
-  var modelThrough = this.definition.modelThrough;
-  var fk = this.definition.keyTo;
-  var fk2 = this.definition.keyThrough;
+  var definition = this.definition;
+  var modelTo = definition.modelTo;
+  var modelThrough = definition.modelThrough;
 
   if (typeof data === 'function' && !done) {
     done = data;
     data = {};
   }
 
-  var self = this.modelInstance;
+  var modelInstance = this.modelInstance;
+
   // First create the target model
   modelTo.create(data, function (err, ac) {
     if (err) {
       return done && done(err, ac);
     }
+    // The primary key for the target model
+    var pk2 = modelTo.dataSource.idName(modelTo.modelName) || 'id';
+    var fk1 = findBelongsTo(modelThrough, definition.modelFrom,
+      definition.keyFrom);
+    var fk2 = findBelongsTo(modelThrough, definition.modelTo, pk2);
     var d = {};
-    d[findBelongsTo(modelThrough, fk)] = self;
-    d[findBelongsTo(modelThrough, fk2)] = ac;
+    d[fk1] = modelInstance[definition.keyFrom];
+    d[fk2] = ac[pk2];
     // Then create the through model
     modelThrough.create(d, function (e) {
       if (e) {
@@ -416,17 +422,28 @@ HasManyThrough.prototype.create = function create(data, done) {
  * @param {Object|ID} acInst The actual instance or id value
  */
 HasManyThrough.prototype.add = function (acInst, done) {
-  var modelThrough = this.definition.modelThrough;
-  var fk = this.definition.keyTo;
-  var fk2 = this.definition.keyThrough;
-  var pk = this.definition.keyFrom;
+  var definition = this.definition;
+  var modelThrough = definition.modelThrough;
+  var modelTo = definition.modelTo;
+  var pk1 = definition.keyFrom;
 
   var data = {};
   var query = {};
-  query[fk] = this[pk];
-  data[findBelongsTo(modelThrough, fk)] = this.modelInstance;
-  query[fk2] = acInst[pk] || acInst;
-  data[findBelongsTo(modelThrough, fk2)] = acInst;
+
+  var fk1 = findBelongsTo(modelThrough, definition.modelFrom,
+    definition.keyFrom);
+
+  // The primary key for the target model
+  var pk2 = modelTo.dataSource.idName(modelTo.modelName) || 'id';
+
+  var fk2 = findBelongsTo(modelThrough, definition.modelTo, pk2);
+
+  query[fk1] = this.modelInstance[pk1];
+  query[fk2] = acInst[pk2] || acInst;
+
+  data[fk1] = this.modelInstance[pk1];
+  data[fk2] = acInst[pk2] || acInst;
+
   // Create an instance of the through model
   modelThrough.findOrCreate({where: query}, data, done);
 };

From 2db43c58e5b0cb4cc3a70b9a13eacebb90139987 Mon Sep 17 00:00:00 2001
From: Raymond Feng <raymond@strongloop.com>
Date: Mon, 16 Jun 2014 01:17:37 -0700
Subject: [PATCH 3/8] Add support for hasOne

---
 lib/relation-definition.js | 139 +++++++++++++++++++++++++++++++++++++
 lib/relations.js           |   4 ++
 test/relations.test.js     |  39 ++++++++++-
 3 files changed, 181 insertions(+), 1 deletion(-)

diff --git a/lib/relation-definition.js b/lib/relation-definition.js
index 09849d12..ae030143 100644
--- a/lib/relation-definition.js
+++ b/lib/relation-definition.js
@@ -656,3 +656,142 @@ RelationDefinition.hasAndBelongsToMany = function hasAndBelongsToMany(modelFrom,
   this.hasMany(modelFrom, modelTo, {as: params.as, through: params.through});
 
 };
+
+/**
+ * HasOne
+ * @param modelFrom
+ * @param modelTo
+ * @param params
+ */
+RelationDefinition.hasOne = function (modelFrom, modelTo, params) {
+  params = params || {};
+  if ('string' === typeof modelTo) {
+    params.as = modelTo;
+    if (params.model) {
+      modelTo = params.model;
+    } else {
+      var modelToName = modelTo.toLowerCase();
+      modelTo = lookupModel(modelFrom.dataSource.modelBuilder.models, modelToName);
+    }
+  }
+
+  var pk = modelFrom.dataSource.idName(modelTo.modelName) || 'id';
+  var relationName = params.as || i8n.camelize(modelTo.modelName, true);
+
+  var fk = params.foreignKey || i8n.camelize(modelFrom.modelName + '_id', true);
+
+  var relationDef = modelFrom.relations[relationName] = new RelationDefinition({
+    name: relationName,
+    type: RelationTypes.hasOne,
+    modelFrom: modelFrom,
+    keyFrom: pk,
+    keyTo: fk,
+    modelTo: modelTo
+  });
+
+  modelFrom.dataSource.defineForeignKey(modelTo.modelName, fk, modelFrom.modelName);
+
+  // Define a property for the scope so that we have 'this' for the scoped methods
+  Object.defineProperty(modelFrom.prototype, relationName, {
+    enumerable: true,
+    configurable: true,
+    get: function() {
+      var relation = new HasOne(relationDef, this);
+      var relationMethod = relation.related.bind(relation)
+      relationMethod.create = relation.create.bind(relation);
+      relationMethod.build = relation.build.bind(relation);
+      return relationMethod;
+    }
+  });
+};
+
+HasOne.prototype.create = function(targetModelData, cb) {
+  var modelTo = this.definition.modelTo;
+  var fk = this.definition.keyTo;
+  var pk = this.definition.keyFrom;
+  var modelInstance = this.modelInstance;
+
+  targetModelData = targetModelData || {};
+  targetModelData[fk] = modelInstance[pk];
+  modelTo.create(targetModelData, function(err, targetModel) {
+    if(!err) {
+      cb && cb(err, targetModel);
+    } else {
+      cb && cb(err);
+    }
+  });
+};
+
+HasOne.prototype.build = function(targetModelData) {
+  var modelTo = this.definition.modelTo;
+  var pk = this.definition.keyFrom;
+  var fk = this.definition.keyTo;
+  targetModelData = targetModelData || {};
+  targetModelData[fk] = this.modelInstance[pk];
+  return new modelTo(targetModelData);
+};
+
+/**
+ * Define the method for the hasOne relation itself
+ * It will support one of the following styles:
+ * - order.customer(refresh, callback): Load the target model instance asynchronously
+ * - order.customer(customer): Synchronous setter of the target model instance
+ * - order.customer(): Synchronous getter of the target model instance
+ *
+ * @param refresh
+ * @param params
+ * @returns {*}
+ */
+HasOne.prototype.related = function (refresh, params) {
+  var modelTo = this.definition.modelTo;
+  var fk = this.definition.keyTo;
+  var pk = this.definition.keyFrom;
+  var modelInstance = this.modelInstance;
+  var relationName = this.definition.name;
+
+  if (arguments.length === 1) {
+    params = refresh;
+    refresh = false;
+  } else if (arguments.length > 2) {
+    throw new Error('Method can\'t be called with more than two arguments');
+  }
+
+  var cachedValue;
+  if (!refresh && modelInstance.__cachedRelations
+    && (modelInstance.__cachedRelations[relationName] !== undefined)) {
+    cachedValue = modelInstance.__cachedRelations[relationName];
+  }
+  if (params instanceof ModelBaseClass) { // acts as setter
+    params[fk] = modelInstance[pk];
+    modelInstance.__cachedRelations[relationName] = params;
+  } else if (typeof params === 'function') { // acts as async getter
+    var cb = params;
+    if (cachedValue === undefined) {
+      var query = {where: {}};
+      query.where[fk] = modelInstance[pk];
+      modelTo.findOne(query, function (err, inst) {
+        if (err) {
+          return cb(err);
+        }
+        if (!inst) {
+          return cb(null, null);
+        }
+        // Check if the foreign key matches the primary key
+        if (inst[fk] === modelInstance[pk]) {
+          cb(null, inst);
+        } else {
+          cb(new Error('Permission denied'));
+        }
+      });
+      return modelInstance[pk];
+    } else {
+      cb(null, cachedValue);
+      return cachedValue;
+    }
+  } else if (params === undefined) { // acts as sync getter
+    return modelInstance[pk];
+  } else { // setter
+    params[fk] = modelInstance[pk];
+    delete modelInstance.__cachedRelations[relationName];
+  }
+};
diff --git a/lib/relations.js b/lib/relations.js
index 8b740359..068bce7f 100644
--- a/lib/relations.js
+++ b/lib/relations.js
@@ -157,3 +157,7 @@ RelationMixin.belongsTo = function (modelTo, params) {
 RelationMixin.hasAndBelongsToMany = function hasAndBelongsToMany(modelTo, params) {
   RelationDefinition.hasAndBelongsToMany(this, modelTo, params);
 };
+
+RelationMixin.hasOne = function hasMany(modelTo, params) {
+  RelationDefinition.hasOne(this, modelTo, params);
+};
diff --git a/test/relations.test.js b/test/relations.test.js
index 7bc3a1b3..d0cd0ea9 100644
--- a/test/relations.test.js
+++ b/test/relations.test.js
@@ -1,7 +1,7 @@
 // This test written in mocha+should.js
 var should = require('./init.js');
 
-var db, Book, Chapter, Author, Reader;
+var db, Book, Chapter, Author, Reader, Publisher;
 
 describe('relations', function () {
   before(function (done) {
@@ -180,6 +180,43 @@ describe('relations', function () {
 
   });
 
+  describe('hasOne', function () {
+    var Supplier, Account;
+
+    before(function () {
+      db = getSchema();
+      Supplier = db.define('Supplier', {name: String});
+      Account = db.define('Account', {accountNo: String});
+    });
+
+    it('can be declared using hasOne method', function () {
+      Supplier.hasOne(Account);
+      Object.keys((new Account()).toObject()).should.include('supplierId');
+      (new Supplier()).account.should.be.an.instanceOf(Function);
+
+    });
+
+    it('can be used to query data', function (done) {
+      // Supplier.hasOne(Account);
+      db.automigrate(function () {
+        Supplier.create({name: 'Supplier 1'}, function (e, supplier) {
+          should.not.exist(e);
+          should.exist(supplier);
+          supplier.account.create({accountNo: 'a01'}, function (err, account) {
+            supplier.account(function (e, act) {
+              should.not.exist(e);
+              should.exist(act);
+              act.should.be.an.instanceOf(Account);
+              supplier.account().should.equal(act.id);
+              done();
+            });
+          });
+        });
+      });
+    });
+
+  });
+
   describe('hasAndBelongsToMany', function () {
     var Article, Tag, ArticleTag;
     it('can be declared', function (done) {

From 046816191df587e686ebd5e6c0c7e330159c643e Mon Sep 17 00:00:00 2001
From: Raymond Feng <raymond@strongloop.com>
Date: Mon, 16 Jun 2014 10:50:42 -0700
Subject: [PATCH 4/8] Clean up scope implementation

---
 lib/scope.js | 208 ++++++++++++++++++++++++++++++++-------------------
 1 file changed, 132 insertions(+), 76 deletions(-)

diff --git a/lib/scope.js b/lib/scope.js
index ac14efc7..185ad0d3 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -6,6 +6,52 @@ var defineCachedRelations = utils.defineCachedRelations;
  */
 exports.defineScope = defineScope;
 
+function ScopeDefinition(definition) {
+  this.sourceModel = definition.sourceModel;
+  this.targetModel = definition.targetModel || definition.sourceModel;
+  this.name = definition.name;
+  this.params = definition.params;
+  this.methods = definition.methods;
+}
+
+ScopeDefinition.prototype.related = function(receiver, scopeParams, condOrRefresh, cb) {
+  var name = this.name;
+  var self = receiver;
+
+  var actualCond = {};
+  var actualRefresh = false;
+  var saveOnCache = true;
+  if (arguments.length === 3) {
+    cb = condOrRefresh;
+  } else if (arguments.length === 4) {
+    if (typeof condOrRefresh === 'boolean') {
+      actualRefresh = condOrRefresh;
+    } else {
+      actualCond = condOrRefresh;
+      actualRefresh = true;
+      saveOnCache = false;
+    }
+  } else {
+    throw new Error('Method can be only called with one or two arguments');
+  }
+
+  if (!self.__cachedRelations || self.__cachedRelations[name] === undefined
+    || actualRefresh) {
+    // It either doesn't hit the cache or refresh is required
+    var params = mergeParams(actualCond, scopeParams);
+    return this.targetModel.find(params, function (err, data) {
+      if (!err && saveOnCache) {
+        defineCachedRelations(self);
+        self.__cachedRelations[name] = data;
+      }
+      cb(err, data);
+    });
+  } else {
+    // Return from cache
+    cb(null, self.__cachedRelations[name]);
+  }
+}
+
 /**
  * Define a scope to the class
  * @param {Model} cls The class where the scope method is added
@@ -22,7 +68,7 @@ function defineScope(cls, targetClass, name, params, methods) {
     cls._scopeMeta = {};
   }
 
-  // only makes sence to add scope in meta if base and target classes
+  // only makes sense to add scope in meta if base and target classes
   // are same
   if (cls === targetClass) {
     cls._scopeMeta[name] = params;
@@ -32,6 +78,14 @@ function defineScope(cls, targetClass, name, params, methods) {
     }
   }
 
+  var definition = new ScopeDefinition({
+    sourceModel: cls,
+    targetModel: targetClass,
+    name: name,
+    params: params,
+    methods: methods
+  });
+
   // Define a property for the scope
   Object.defineProperty(cls, name, {
     enumerable: false,
@@ -49,42 +103,18 @@ function defineScope(cls, targetClass, name, params, methods) {
      */
     get: function () {
       var self = this;
-      var f = function caller(condOrRefresh, cb) {
-        var actualCond = {};
-        var actualRefresh = false;
-        var saveOnCache = true;
-        if (arguments.length === 1) {
-          cb = condOrRefresh;
-        } else if (arguments.length === 2) {
-          if (typeof condOrRefresh === 'boolean') {
-            actualRefresh = condOrRefresh;
-          } else {
-            actualCond = condOrRefresh;
-            actualRefresh = true;
-            saveOnCache = false;
-          }
+      var f = function(condOrRefresh, cb) {
+        if(arguments.length === 1) {
+          definition.related(self, f._scope, condOrRefresh);
         } else {
-          throw new Error('Method can be only called with one or two arguments');
-        }
-
-        if (!self.__cachedRelations || self.__cachedRelations[name] === undefined
-          || actualRefresh) {
-          // It either doesn't hit the cache or reresh is required
-          var params = mergeParams(actualCond, caller._scope);
-          return targetClass.find(params, function (err, data) {
-            if (!err && saveOnCache) {
-              defineCachedRelations(self);
-              self.__cachedRelations[name] = data;
-            }
-            cb(err, data);
-          });
-        } else {
-          // Return from cache
-          cb(null, self.__cachedRelations[name]);
+          definition.related(self, f._scope, condOrRefresh, cb);
         }
       };
-      f._scope = typeof params === 'function' ? params.call(this) : params;
-      f._targetClass = targetClass.modelName;
+
+      f._scope = typeof definition.params === 'function' ?
+        definition.params.call(self) : definition.params;
+
+      f._targetClass = definition.targetModel.modelName;
       if (f._scope.collect) {
         f._targetClass = i8n.capitalize(f._scope.collect);
       }
@@ -92,11 +122,14 @@ function defineScope(cls, targetClass, name, params, methods) {
       f.build = build;
       f.create = create;
       f.destroyAll = destroyAll;
-      for (var i in methods) {
-        f[i] = methods[i].bind(this);
+      for (var i in definition.methods) {
+        f[i] = definition.methods[i].bind(self);
       }
 
-      // define sub-scopes
+      // Define scope-chaining, such as
+      // Station.scope('active', {where: {isActive: true}});
+      // Station.scope('subway', {where: {isUndeground: true}});
+      // Station.active.subway(cb);
       Object.keys(targetClass._scopeMeta).forEach(function (name) {
         Object.defineProperty(f, name, {
           enumerable: false,
@@ -105,7 +138,7 @@ function defineScope(cls, targetClass, name, params, methods) {
             return f;
           }
         });
-      }.bind(this));
+      }.bind(self));
       return f;
     }
   });
@@ -152,7 +185,13 @@ function defineScope(cls, targetClass, name, params, methods) {
 
   // and it should have create/build methods with binded thisModelNameId param
   function build(data) {
-    return new targetClass(mergeParams(this._scope, {where: data || {}}).where);
+    data = data || {};
+    var params = mergeParams(this._scope, {where: data}).where;
+    delete params['and'];
+    delete params['or'];
+    delete params['nor'];
+
+    return new targetClass(params);
   }
 
   function create(data, cb) {
@@ -187,53 +226,70 @@ function defineScope(cls, targetClass, name, params, methods) {
       }
     });
   }
-
-  function mergeParams(base, update) {
-    base = base || {};
-    if (update.where) {
-      base.where = merge(base.where, update.where);
-    }
-    if (update.include) {
-      base.include = update.include;
-    }
-    if (update.collect) {
-      base.collect = update.collect;
-    }
-
-    // overwrite order
-    if (update.order) {
-      base.order = update.order;
-    }
-
-    if(update.limit !== undefined) {
-      base.limit = update.limit;
-    }
-    if(update.skip !== undefined) {
-      base.skip = update.skip;
-    }
-    if(update.offset !== undefined) {
-      base.offset = update.offset;
-    }
-    if(update.fields !== undefined) {
-      base.fields = update.fields;
-    }
-    return base;
-
-  }
 }
 
-/**
+/*!
  * Merge `base` and `update` params
  * @param {Object} base - base object (updating this object)
  * @param {Object} update - object with new data to update base
  * @returns {Object} `base`
+ * @private
  */
-function merge(base, update) {
+function mergeWhere(base, update) {
   base = base || {};
   if (update) {
-    Object.keys(update).forEach(function (key) {
+    var keys = Object.keys(update);
+    for (var k = 0; k < keys.length; k++) {
+      var key = keys[k];
       base[key] = update[key];
-    });
+    }
+  }
+  return base;
+}
+
+/*!
+ * Merge query parameters
+ * @param base
+ * @param update
+ * @returns {*|{}}
+ * @private
+ */
+function mergeParams(base, update) {
+  if (!update) {
+    return;
+  }
+  base = base || {};
+  if (update.where) {
+    base.where = mergeWhere(base.where, update.where);
+  }
+
+  // Overwrite inclusion
+  if (update.include) {
+    base.include = update.include;
+  }
+  if (update.collect) {
+    base.collect = update.collect;
+  }
+
+  // overwrite order
+  if (update.order) {
+    base.order = update.order;
+  }
+
+  // overwrite pagination
+  if (update.limit !== undefined) {
+    base.limit = update.limit;
+  }
+  if (update.skip !== undefined) {
+    base.skip = update.skip;
+  }
+  if (update.offset !== undefined) {
+    base.offset = update.offset;
+  }
+
+  // Overwrite fields
+  if (update.fields !== undefined) {
+    base.fields = update.fields;
   }
   return base;
 }

From e2ab9ccc931aaa7d2512c054afefe46d1a44eb6b Mon Sep 17 00:00:00 2001
From: Raymond Feng <raymond@strongloop.com>
Date: Mon, 16 Jun 2014 13:46:17 -0700
Subject: [PATCH 5/8] Adding back the remoting metadata

---
 lib/relation-definition.js | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/lib/relation-definition.js b/lib/relation-definition.js
index ae030143..38c52c93 100644
--- a/lib/relation-definition.js
+++ b/lib/relation-definition.js
@@ -520,12 +520,30 @@ RelationDefinition.belongsTo = function (modelFrom, modelTo, params) {
     configurable: true,
     get: function() {
       var relation = new BelongsTo(relationDef, this);
-      var relationMethod = relation.related.bind(relation)
+      var relationMethod = relation.related.bind(relation);
       relationMethod.create = relation.create.bind(relation);
       relationMethod.build = relation.build.bind(relation);
+      relationMethod._targetClass = relationDef.modelTo.modelName;
       return relationMethod;
     }
   });
+
+  // Wrap the property into a function for remoting
+  // so that it can be accessed as /api/<model>/<id>/<belongsToRelationName>
+  // For example, /api/orders/1/customer
+  var fn = function() {
+    var f = this[relationName];
+    f.apply(this, arguments);
+  };
+
+  fn.shared = true;
+  fn.http = {verb: 'get', path: '/' + relationName};
+  fn.accepts = {arg: 'refresh', type: 'boolean', http: {source: 'query'}};
+  fn.description = 'Fetches belongsTo relation ' + relationName;
+  fn.returns = {arg: relationName, type: 'object', root: true};
+
+  modelFrom.prototype['__get__' + relationName] = fn;
+
 };
 
 BelongsTo.prototype.create = function(targetModelData, cb) {

From 177752e144a6f53febc5342588bb20ad7caa4d29 Mon Sep 17 00:00:00 2001
From: Raymond Feng <raymond@strongloop.com>
Date: Thu, 19 Jun 2014 11:13:24 -0700
Subject: [PATCH 6/8] Add more jsdocs

---
 lib/relation-definition.js | 49 ++++++++++++++++++++++++++++----------
 test/relations.test.js     |  1 -
 2 files changed, 36 insertions(+), 14 deletions(-)

diff --git a/lib/relation-definition.js b/lib/relation-definition.js
index 38c52c93..13366d7a 100644
--- a/lib/relation-definition.js
+++ b/lib/relation-definition.js
@@ -631,17 +631,19 @@ BelongsTo.prototype.related = function (refresh, params) {
 };
 
 /**
- * A hasAndBelongsToMany relation creates a direct many-to-many connection with another model, with no intervening model.
- * For example, if your application includes users and groups, with each group having many users and each user appearing
- * in many groups, you could declare the models this way:
+ * A hasAndBelongsToMany relation creates a direct many-to-many connection with
+ * another model, with no intervening model. For example, if your application
+ * includes users and groups, with each group having many users and each user
+ * appearing in many groups, you could declare the models this way:
  * ```
  *  User.hasAndBelongsToMany('groups', {model: Group, foreignKey: 'groupId'});
  * ```
  * 
- * @param {String|Object} modelTo Model object (or String name of model) to which you are creating the relationship.
- * the relation
+ * @param {String|Object} modelTo Model object (or String name of model) to
+ * which you are creating the relationship.
  * @options {Object} params Configuration parameters; see below.
- * @property {String} as Name of the property in the referring model that corresponds to the foreign key field in the related model.
+ * @property {String} as Name of the property in the referring model that
+ * corresponds to the foreign key field in the related model.
  * @property {String} foreignKey Property name of foreign key field.
  * @property {Object} model Model object
  */
@@ -676,10 +678,19 @@ RelationDefinition.hasAndBelongsToMany = function hasAndBelongsToMany(modelFrom,
 };
 
 /**
- * HasOne
- * @param modelFrom
- * @param modelTo
- * @param params
+ * A HasOne relation creates a one-to-one connection from modelFrom to modelTo.
+ * This relation indicates that each instance of a model contains or possesses
+ * one instance of another model. For example, each supplier in your application
+ * has only one account.
+ *
+ * @param {Function} modelFrom The declaring model class
+ * @param {String|Function} modelTo Model object (or String name of model) to
+ * which you are creating the relationship.
+ * @options {Object} params Configuration parameters; see below.
+ * @property {String} as Name of the property in the referring model that
+ * corresponds to the foreign key field in the related model.
+ * @property {String} foreignKey Property name of foreign key field.
+ * @property {Object} model Model object
  */
 RelationDefinition.hasOne = function (modelFrom, modelTo, params) {
   params = params || {};
@@ -723,6 +734,13 @@ RelationDefinition.hasOne = function (modelFrom, modelTo, params) {
   });
 };
 
+/**
+ * Create a target model instance
+ * @param {Object} targetModelData The target model data
+ * @callback {Function} [cb] Callback function
+ * @param {String|Object} err Error string or object
+ * @param {Object} The newly created target model instance
+ */
 HasOne.prototype.create = function(targetModelData, cb) {
   var modelTo = this.definition.modelTo;
   var fk = this.definition.keyTo;
@@ -740,6 +758,11 @@ HasOne.prototype.create = function(targetModelData, cb) {
   });
 };
 
+/**
+ * Build a target model instance
+ * @param {Object} targetModelData The target model data
+ * @returns {Object} The newly built target model instance
+ */
 HasOne.prototype.build = function(targetModelData) {
   var modelTo = this.definition.modelTo;
   var pk = this.definition.keyFrom;
@@ -756,9 +779,9 @@ HasOne.prototype.build = function(targetModelData) {
  * - order.customer(customer): Synchronous setter of the target model instance
  * - order.customer(): Synchronous getter of the target model instance
  *
- * @param refresh
- * @param params
- * @returns {*}
+ * @param {Boolean} refresh Reload from the data source
+ * @param {Object|Function} params Query parameters
+ * @returns {Object}
  */
 HasOne.prototype.related = function (refresh, params) {
   var modelTo = this.definition.modelTo;
diff --git a/test/relations.test.js b/test/relations.test.js
index d0cd0ea9..4e1f5873 100644
--- a/test/relations.test.js
+++ b/test/relations.test.js
@@ -193,7 +193,6 @@ describe('relations', function () {
       Supplier.hasOne(Account);
       Object.keys((new Account()).toObject()).should.include('supplierId');
       (new Supplier()).account.should.be.an.instanceOf(Function);
-
     });
 
     it('can be used to query data', function (done) {

From 18333522381c0dfab35f241421489900ee95a402 Mon Sep 17 00:00:00 2001
From: Raymond Feng <raymond@strongloop.com>
Date: Thu, 19 Jun 2014 12:00:49 -0700
Subject: [PATCH 7/8] More clean up for the scope processing

---
 lib/scope.js       | 93 ++++++++++++++++++++++------------------------
 test/scope.test.js |  2 +-
 2 files changed, 45 insertions(+), 50 deletions(-)

diff --git a/lib/scope.js b/lib/scope.js
index 185ad0d3..8a4485df 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -38,7 +38,7 @@ ScopeDefinition.prototype.related = function(receiver, scopeParams, condOrRefres
   if (!self.__cachedRelations || self.__cachedRelations[name] === undefined
     || actualRefresh) {
     // It either doesn't hit the cache or refresh is required
-    var params = mergeParams(actualCond, scopeParams);
+    var params = mergeQuery(actualCond, scopeParams);
     return this.targetModel.find(params, function (err, data) {
       if (!err && saveOnCache) {
         defineCachedRelations(self);
@@ -134,7 +134,7 @@ function defineScope(cls, targetClass, name, params, methods) {
         Object.defineProperty(f, name, {
           enumerable: false,
           get: function () {
-            mergeParams(f._scope, targetClass._scopeMeta[name]);
+            mergeQuery(f._scope, targetClass._scopeMeta[name]);
             return f;
           }
         });
@@ -183,15 +183,40 @@ function defineScope(cls, targetClass, name, params, methods) {
 
   cls['__delete__' + name] = fn_delete;
 
+  /*
+   * Extracting fixed property values for the scope from the where clause into
+   * the data object
+   *
+   * @param {Object} The data object
+   * @param {Object} The where clause
+   */
+  function setScopeValuesFromWhere(data, where) {
+    for (var i in where) {
+      if (i === 'and') {
+        // Find fixed property values from each subclauses
+        for (var w = 0, n = where[i].length; w < n; w++) {
+          setScopeValuesFromWhere(data, where[i][w]);
+        }
+        continue;
+      }
+      var prop = targetClass.definition.properties[i];
+      if (prop) {
+        var val = where[i];
+        if (typeof val !== 'object' || val instanceof prop.type) {
+          // Only pick the {propertyName: propertyValue}
+          data[i] = where[i];
+        }
+      }
+    }
+  }
+
   // and it should have create/build methods with binded thisModelNameId param
   function build(data) {
     data = data || {};
-    var params = mergeParams(this._scope, {where: data}).where;
-    delete params['and'];
-    delete params['or'];
-    delete params['nor'];
-
-    return new targetClass(params);
+    // Find all fixed property values for the scope
+    var where = (this._scope && this._scope.where) || {};
+    setScopeValuesFromWhere(data, where);
+    return new targetClass(data);
   }
 
   function create(data, cb) {
@@ -209,58 +234,28 @@ function defineScope(cls, targetClass, name, params, methods) {
    - If fetching the Elements on which destroyAll is called results in an error
    */
   function destroyAll(cb) {
-    targetClass.find(this._scope, function (err, data) {
-      if (err) {
-        cb(err);
-      } else {
-        (function loopOfDestruction(data) {
-          if (data.length > 0) {
-            data.shift().destroy(function (err) {
-              if (err && cb) cb(err);
-              loopOfDestruction(data);
-            });
-          } else {
-            if (cb) cb();
-          }
-        }(data));
-      }
-    });
+    targetClass.destroyAll(this._scope, cb);
   }
 }
 
-/*!
- * Merge `base` and `update` params
- * @param {Object} base - base object (updating this object)
- * @param {Object} update - object with new data to update base
- * @returns {Object} `base`
- * @private
- */
-function mergeWhere(base, update) {
-  base = base || {};
-  if (update) {
-    var keys = Object.keys(update);
-    for (var k = 0; k < keys.length; k++) {
-      var key = keys[k];
-      base[key] = update[key];
-    }
-  }
-  return base;
-}
-
 /*!
  * Merge query parameters
- * @param base
- * @param update
- * @returns {*|{}}
+ * @param {Object} base The base object to contain the merged results
+ * @param {Object} update The object containing updates to be merged
+ * @returns {*|Object} The base object
  * @private
  */
-function mergeParams(base, update) {
+function mergeQuery(base, update) {
   if (!update) {
     return;
   }
   base = base || {};
-  if (update.where) {
-    base.where = mergeWhere(base.where, update.where);
+  if (update.where && Object.keys(update.where).length > 0) {
+    if (base.where && Object.keys(base.where).length > 0) {
+      base.where = {and: [base.where, update.where]};
+    } else {
+      base.where = update.where;
+    }
   }
 
   // Overwrite inclusion
diff --git a/test/scope.test.js b/test/scope.test.js
index d927bcc7..ecaa8727 100644
--- a/test/scope.test.js
+++ b/test/scope.test.js
@@ -3,7 +3,7 @@ var should = require('./init.js');
 
 var db, Railway, Station;
 
-describe('sc0pe', function () {
+describe('scope', function () {
 
   before(function () {
     db = getSchema();

From 27f4c1b7b437f1d15efd18876f3ed1a9fd4d39ad Mon Sep 17 00:00:00 2001
From: Raymond Feng <raymond@strongloop.com>
Date: Thu, 19 Jun 2014 15:09:19 -0700
Subject: [PATCH 8/8] Fix the error msg

---
 lib/list.js | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/lib/list.js b/lib/list.js
index 3e6faa1e..4c4158eb 100644
--- a/lib/list.js
+++ b/lib/list.js
@@ -13,7 +13,7 @@ function List(items, itemType, parent) {
     try {
       items = JSON.parse(items);
     } catch (e) {
-      throw new Error('could not create List from JSON string: ', items);
+      throw new Error(util.format('could not create List from JSON string: %j', items));
     }
   }
 
@@ -22,7 +22,7 @@ function List(items, itemType, parent) {
 
   items = items || [];
   if (!Array.isArray(items)) {
-    throw new Error('Items must be an array: ' + items);
+    throw new Error(util.format('Items must be an array: %j', items));
   }
 
   if(!itemType) {
@@ -92,12 +92,3 @@ List.prototype.toString = function () {
   return JSON.stringify(this.toJSON());
 };
 
-/*
- var strArray = new List(['1', 2], String);
- strArray.push(3);
- console.log(strArray);
- console.log(strArray.length);
-
- console.log(strArray.toJSON());
- console.log(strArray.toString());
- */