fixes #204 thanks to @bpartridge

lib/associations/has-many-double-linked.js

@@ -51,7 +51,11 @@ module.exports = (function() {
         var chainer             = new Utils.QueryChainer
           , association         = self.__factory.target.associations[self.__factory.associationAccessor]
           , foreignIdentifier   = association.isSelfAssociation ? association.foreignIdentifier : association.identifier
-          , unassociatedObjects = newAssociations.filter(function(obj) { return !obj.equalsOneOf(oldAssociations) })
+          , unassociatedObjects = newAssociations.filter(function (obj) { 
+              return !Utils._.find(oldAssociations, function (old) {
+                return obj.id === old.id
+              }) 
+            })
 
         unassociatedObjects.forEach(function(unassociatedObject) {
           var attributes = {}
@@ -69,6 +73,20 @@ module.exports = (function() {
       })
   }
 
+  HasManyDoubleLinked.prototype.injectAdder = function(emitterProxy, newAssociation) {
+    var attributes = {}
+      , association         = this.__factory.target.associations[this.__factory.associationAccessor]
+      , foreignIdentifier   = association.isSelfAssociation ? association.foreignIdentifier : association.identifier;
+
+    attributes[this.__factory.identifier] = this.instance.id
+    attributes[foreignIdentifier] = newAssociation.id
+
+    this.__factory.connectorDAO.create(attributes)
+      .success(function() { emitterProxy.emit('success', newAssociation) })
+      .error(function(err) { emitterProxy.emit('error', err) })
+      .on('sql', function(sql) { emitterProxy.emit('sql', sql) })
+  }
+
   // private
 
   var destroyObsoleteAssociations = function(oldAssociations, newAssociations) {
@@ -77,7 +95,12 @@ module.exports = (function() {
     return new Utils.CustomEventEmitter(function(emitter) {
       var chainer = new Utils.QueryChainer()
       var foreignIdentifier = self.__factory.target.associations[self.__factory.associationAccessor].identifier
-      var obsoleteAssociations = oldAssociations.filter(function(obj) { return !obj.equalsOneOf(newAssociations) })
+      var obsoleteAssociations = Utils._.filter(oldAssociations, function (old) {
+        // Return only those old associations that are not found in new
+        return !Utils._.find(newAssociations, function (obj) {
+          return obj.id === old.id
+        })
+      })
 
       if (obsoleteAssociations.length === 0) {
         return emitter.emit('success', null)

lib/associations/has-many-single-linked.js

@@ -19,15 +19,25 @@ module.exports = (function() {
     var self    = this
       , options = this.__factory.options
       , chainer = new Utils.QueryChainer()
+      , obsoleteAssociations = oldAssociations.filter(function (old) { 
+          return !Utils._.find(newAssociations, function (obj) {
+            return obj.id === old.id
+          }) 
+        })
+      , unassociatedObjects = newAssociations.filter(function (obj) { 
+          return !Utils._.find(oldAssociations, function (old) {
+            return obj.id === old.id
+          }) 
+        })
 
     // clear the old associations
-    oldAssociations.forEach(function(associatedObject) {
+    obsoleteAssociations.forEach(function(associatedObject) {
       associatedObject[self.__factory.identifier] = null
       chainer.add(associatedObject.save())
     })
 
     // set the new associations
-    newAssociations.forEach(function(associatedObject) {
+    unassociatedObjects.forEach(function(associatedObject) {
       associatedObject[self.__factory.identifier] = self.instance.id
       chainer.add(associatedObject.save())
     })
@@ -38,5 +48,14 @@ module.exports = (function() {
       .error(function(err) { emitter.emit('error', err) })
   }
 
+  HasManySingleLinked.prototype.injectAdder = function(emitterProxy, newAssociation) {
+    newAssociation[this.__factory.identifier] = this.instance.id
+
+    newAssociation.save()
+      .success(function() { emitterProxy.emit('success', newAssociation) })
+      .error(function(err) { emitterProxy.emit('error', err) })
+      .on('sql', function(sql) { emitterProxy.emit('sql', sql) })
+  }
+
   return HasManySingleLinked
 })()

lib/associations/has-many.js

@@ -151,19 +151,18 @@ module.exports = (function() {
 
     obj[this.accessors.add] = function(newAssociatedObject) {
       var instance = this
-      var customEventEmitter = new Utils.CustomEventEmitter(function() {
-        instance[self.accessors.get]()
-          .error(function(err){ customEventEmitter.emit('error', err)})
+      return new Utils.CustomEventEmitter(function(emitter) {
+        instance[self.accessors.get]({ where: { id: newAssociatedObject.id }})
+          .error(function(err){ emitter.emit('error', err)})
           .success(function(currentAssociatedObjects) {
-            if (!newAssociatedObject.equalsOneOf(currentAssociatedObjects))
-              currentAssociatedObjects.push(newAssociatedObject)
-
-            instance[self.accessors.set](currentAssociatedObjects)
-              .success(function(instances) { customEventEmitter.emit('success', instances) })
-              .error(function(err) { customEventEmitter.emit('error', err) })
+            if (currentAssociatedObjects.length === 0) {
+              var Class = self.connectorDAO ? HasManyMultiLinked : HasManySingleLinked
+              new Class(self, instance).injectAdder(emitter, newAssociatedObject)
+            } else {
+              emitter.emit('success', newAssociatedObject);
+            }
           })
-      })
-      return customEventEmitter.run()
+      }).run()
     }
 
     obj[this.accessors.remove] = function(oldAssociatedObject) {