merge: added selective save

lib/associations/belongs-to.js

@@ -44,7 +44,9 @@ module.exports = (function() {
 
     obj[accessor] = function(associatedObject) {
       obj[self.identifier] = associatedObject ? associatedObject.id : null
-      return obj.save()
+
+      // passes the changed field to save, so only that field get updated.
+      return obj.save([self.identifier])
     }
 
     return this

lib/dao.js

@@ -81,7 +81,20 @@ module.exports = (function() {
     }
   })
 
-  DAO.prototype.save = function() {
+  // if an array with field names is passed to save()
+  // only those fields will be updated
+  DAO.prototype.save = function(fields) {
+    var self   = this
+      , values = fields ? {} : this.values;
+
+    if(fields) {
+      fields.forEach(function(field) {
+        if(self.values[field]) {
+          values[field] = self.values[field]
+        }
+      });
+    }
+
     var updatedAtAttr = this.__options.underscored ? 'updated_at' : 'updatedAt'
 
     if(this.__options.timestamps && this.hasOwnProperty(updatedAtAttr))
@@ -92,7 +105,7 @@ module.exports = (function() {
     } else {
       var identifier = this.__options.hasPrimaryKeys ? this.primaryKeyValues : this.id
         , tableName  = this.__factory.tableName
-        , query      = this.QueryInterface.update(this, tableName, this.values, identifier)
+        , query      = this.QueryInterface.update(this, tableName, values, identifier)
 
       return query
     }

spec-jasmine/dao.spec.js

@@ -333,6 +333,51 @@ describe('DAO', function() {
       })
 
       describe('save', function() {
+        it('only updates fields in passed array', function() {
+          var user   = null
+            , user2  = null
+            , userId = null
+            , date   = new Date(1990, 01, 01)
+
+          Helpers.async(function(done) {
+            User.create({
+              username: 'foo',
+              birthDate: new Date()
+            }).success(function(_user) {
+              user = _user
+              done()
+            }).error(function(err) {
+              console.log(err)
+            })
+          })
+
+          Helpers.async(function(done) {
+            user.username = 'fizz'
+            user.birthDate = date
+
+            done()
+          })
+
+          Helpers.async(function(done) {
+            user.save(['username']).success(function(){
+              // re-select user
+              User.find(user.id).success(function(_user2) {
+                user2 = _user2
+                done()
+              })
+            })
+          })
+
+          Helpers.async(function(done) {
+            // name should have changed
+            expect(user2.username).toEqual('fizz')
+            // bio should be unchanged
+            expect(user2.birthDate).toNotEqual(date)
+
+            done()
+          })
+        })
+
         it("stores an entry in the database", function() {
           var username = 'user'
             , user     = User.build({