add function takes care about parent existence. fix #426, #434

src/Container.js

@@ -60,8 +60,11 @@
          * @returns {Container}
          */
         add: function(child) {
+            if (child.getParent()) {
+                child.moveTo(this);
+                return;
+            }
             var children = this.children;
-
             this._validateAdd(child);
             child.index = children.length;
             child.parent = this;

test/unit/Container-test.js

@@ -1352,6 +1352,41 @@ suite('Container', function() {
         assert.equal(blueGroup.getZIndex(), 1, 'blue group should have zindex 1 after relayering');
         assert.equal(greenGroup.getZIndex(), 0, 'green group should have zindex 0 after relayering');
 
+        layer.draw();
+    });
+
+    // ======================================================
+    test('add and moveTo should work same way (depend on parent)', function() {
+        var stage = addStage();
+        var layer = new Kinetic.Layer();
+        var greenGroup = new Kinetic.Group();
+        var blueGroup = new Kinetic.Group();
+
+        var bluecircle = new Kinetic.Circle({
+            x: 200,
+            y: stage.getHeight() / 2,
+            radius: 70,
+            fill: 'blue',
+            stroke: 'black',
+            strokeWidth: 4
+        });
+
+        bluecircle.moveTo(blueGroup);
+
+        layer.add(blueGroup);
+        layer.add(greenGroup);
+        stage.add(layer);
+
+        assert.equal(blueGroup.getChildren().length, 1, 'blue group should have only one children');
+        blueGroup.add(bluecircle);
+        assert.equal(blueGroup.getChildren().length, 1, 'blue group should have only one children after adding node twice');
+
+        greenGroup.add(bluecircle);
+        assert.equal(blueGroup.getChildren().length, 0, 'blue group should not have children');
+        assert.equal(greenGroup.getChildren().length, 1, 'green group should have only one children');
+
+
+
         layer.draw();
     });