Instance-level property-change events.

TODO.md

@@ -4,8 +4,8 @@ TODO
 * Data store's should be able to extend their Model API when necessary.
 * Fire data-driven events (EventEmitter2)
 
-  model.on('change', function(name, value, old) {});
-  model.on('change:name', function(value, old) {});
+  √ model.on('change', function(name, value, old) {});
+  √ model.on('change:name', function(value, old) {});
   model.on('delete', function(model) {});
 
 * Fire Model-type level data-driven events:

lib/model.js

@@ -353,6 +353,8 @@ Model.create = function(options) {
         return value;
       },
       set: function(value) {
+        var oldValue = this.fields[key];
+
         // Note: setting value to undefined resets the property to its default
         // value, if configured.
         if (value === undefined) {
@@ -369,13 +371,14 @@ Model.create = function(options) {
             return;
           }
         }
-
-        if (setters[key]) {
-          // Property was configured with a setter -- pass the value through it.
-          this.fields[key] = setters[key](value);
 
-        } else {
-          this.fields[key] = value;
+        // If property was configured with a setter -- pass the value through it.
+        this.fields[key] = setters[key] ? setters[key](value) : value ;
+        var newValue = this.fields[key];
+
+        if (oldValue !== newValue) {
+          this.emit('change', key, oldValue, newValue);
+          this.emit('change:' + key, oldValue, newValue);
         }
       },
       enumerable: true,

test/model.test.js

@@ -105,6 +105,31 @@ describe('Model', function() {
     assert.equal(30, model.age);
   });
 
+  it('should emit events when properties change', function(done) {
+    var model = new TestModel1();
+
+    model.on('change', function(property, old, value) {
+      assert.equal('username', property);
+      assert.equal(undefined, old);
+      assert.equal('radical', value);
+      done();
+    });
+
+    model.username = 'radical';
+  });
+
+  it('should emit events when a specific property change', function(done) {
+    var model = new TestModel1();
+
+    model.on('change:username', function(old, value) {
+      assert.equal(undefined, old);
+      assert.equal('radical', value);
+      done();
+    });
+
+    model.username = 'radical';
+  });
+
   it('should serialize models to JSON', function() {
     var model = new TestModel1(); // id == 6
     var json = model.toJSON();