Refactor the serialize/deserialize into two functions

lib/connectors/memory.js

@@ -51,6 +51,24 @@ Memory.prototype.connect = function (callback) {
   }
 };
 
+function serialize(obj) {
+  if(obj === null || obj === undefined) {
+    return obj;
+  }
+  return JSON.stringify(obj);
+}
+
+function deserialize(dbObj) {
+  if(dbObj === null || dbObj === undefined) {
+    return dbObj;
+  }
+  if(typeof dbObj === 'string') {
+    return JSON.parse(dbObj);
+  } else {
+    return dbObj;
+  }
+}
+
 Memory.prototype.loadFromFile = function(callback) {
   var self = this;
   if (self.settings.file) {
@@ -142,7 +160,7 @@ Memory.prototype.create = function create(model, data, callback) {
   if(!this.cache[model]) {
     this.cache[model] = {};
   }
-  this.cache[model][id] = JSON.stringify(data);
+  this.cache[model][id] = serialize(data);
   this.saveToFile(id, callback);
 };
 
@@ -161,7 +179,7 @@ Memory.prototype.updateOrCreate = function (model, data, callback) {
 };
 
 Memory.prototype.save = function save(model, data, callback) {
-  this.cache[model][this.getIdValue(model, data)] = JSON.stringify(data);
+  this.cache[model][this.getIdValue(model, data)] = serialize(data);
   this.saveToFile(data, callback);
 };
 
@@ -185,7 +203,7 @@ Memory.prototype.destroy = function destroy(model, id, callback) {
 
 Memory.prototype.fromDb = function (model, data) {
   if (!data) return null;
-  data = JSON.parse(data);
+  data = deserialize(data);
   var props = this._models[model].properties;
   for (var key in data) {
     var val = data[key];
@@ -374,8 +392,8 @@ Memory.prototype.updateAttributes = function updateAttributes(model, id, data, c
   this.setIdValue(model, data, id);
 
   var cachedModels = this.cache[model];
-  var modelAsString = cachedModels && this.cache[model][id];
+  var modelData = cachedModels && this.cache[model][id];
-  var modelData = modelAsString && JSON.parse(modelAsString);
+  modelData = modelData && deserialize(modelData);
 
   if (modelData) {
     this.save(model, merge(modelData, data), cb);