Allow custom scopeMethods option (obj/fn) for relation scopes

lib/relation-definition.js

@@ -52,7 +52,25 @@ function normalizeType(type) {
     }
   }
   return null;
-}
+};
+
+function extendScopeMethods(definition, scopeMethods, ext) {
+  var relationClass = RelationClasses[definition.type];
+  if (definition.type === RelationTypes.hasMany && definition.modelThrough) {
+    relationClass = RelationClasses.hasManyThrough;
+  }
+  if (typeof ext === 'function') {
+    ext.call(definition, scopeMethods, relationClass);
+  } else if (typeof ext === 'object') {
+    for (var key in ext) {
+      scopeMethods[key] = function () {
+        var relation = new relationClass(definition, this);
+        return ext[key].apply(relation, arguments);
+      };
+    }
+  }
+  return scopeMethods;
+};
 
 /**
  * Relation definition class.  Use to define relationships between models.
@@ -518,7 +536,7 @@ RelationDefinition.hasMany = function hasMany(modelFrom, modelTo, params) {
     }
     
     return filter;
-  }, scopeMethods);
+  }, extendScopeMethods(definition, scopeMethods, params.scopeMethods));
 
 };
 
@@ -1536,12 +1554,14 @@ RelationDefinition.embedsMany = function embedsMany(modelFrom, modelTo, params)
   scopeMethods.create = scopeMethod(definition, 'create');
   scopeMethods.build = scopeMethod(definition, 'build');
   
+  scopeMethods.related = scopeMethod(definition, 'related'); // bound to definition
+  
   // Mix the property and scoped methods into the prototype class
   var scopeDefinition = defineScope(modelFrom.prototype, modelTo, accessorName, function () {
     return {};
-  }, scopeMethods);
+  }, extendScopeMethods(definition, scopeMethods, params.scopeMethods));
 
-  scopeDefinition.related = scopeMethod(definition, 'related'); // bound to definition
+  scopeDefinition.related = scopeMethods.related;
 };
 
 EmbedsMany.prototype.related = function(receiver, scopeParams, condOrRefresh, cb) {
@@ -1934,12 +1954,14 @@ RelationDefinition.referencesMany = function referencesMany(modelFrom, modelTo,
   scopeMethods.create = scopeMethod(definition, 'create');
   scopeMethods.build = scopeMethod(definition, 'build');
   
+  scopeMethods.related = scopeMethod(definition, 'related');
+  
   // Mix the property and scoped methods into the prototype class
   var scopeDefinition = defineScope(modelFrom.prototype, modelTo, relationName, function () {
     return {};
-  }, scopeMethods);
+  }, extendScopeMethods(definition, scopeMethods, params.scopeMethods));
   
-  scopeDefinition.related = scopeMethod(definition, 'related'); // bound to definition
+  scopeDefinition.related = scopeMethods.related; // bound to definition
 };
 
 ReferencesMany.prototype.related = function(receiver, scopeParams, condOrRefresh, cb) {

test/relations.test.js

@@ -1858,7 +1858,16 @@ describe('relations', function () {
     });
 
     it('can be declared', function (done) {
-      Category.referencesMany(Product);
+      Category.referencesMany(Product, { scopeMethods: {
+        reverse: function(cb) {
+          var modelInstance = this.modelInstance;
+          var fk = this.definition.keyFrom;
+          var ids = modelInstance[fk] || [];
+          modelInstance.updateAttribute(fk, ids.reverse(), function(err, inst) {
+            cb(err, inst[fk] || []);
+          });
+        }
+      } });
       db.automigrate(done);
     });
     
@@ -1887,7 +1896,7 @@ describe('relations', function () {
       });
     });
     
-    it('should not create duplicate record on scope', function (done) {
+    it('should not allow duplicate record on scope', function (done) {
       Category.findOne(function(err, cat) {
         cat.productIds = [product2.id, product2.id];
         cat.save(function(err, p) {
@@ -2035,14 +2044,25 @@ describe('relations', function () {
       });
     });
     
+    it('should allow custom scope methods - reverse', function(done) {
+      Category.findOne(function(err, cat) {
+        cat.products.reverse(function(err, ids) {
+          var expected = [product3.id, product2.id];
+          ids.should.eql(expected);
+          cat.productIds.should.eql(expected);
+          done();
+        });
+      })
+    });
+    
     it('should include related items from scope', function(done) {
       Category.find({ include: 'products' }, function(err, categories) {
         categories.should.have.length(1);
         var cat = categories[0].toObject();
         cat.name.should.equal('Category A');
         cat.products.should.have.length(2);
-        cat.products[0].id.should.eql(product2.id);
-        cat.products[1].id.should.eql(product3.id);
+        cat.products[0].id.should.eql(product3.id);
+        cat.products[1].id.should.eql(product2.id);
         done();
       });
     });