refactor(NgClass): remove pipes from property bindings

Author: pkozlowski-opensource

modules/angular2/src/directives/class.ts

@@ -1,13 +1,18 @@
-import {Directive} from 'angular2/annotations';
+import {Directive, onCheck} from 'angular2/annotations';
 import {ElementRef} from 'angular2/core';
-
+import {PipeRegistry} from 'angular2/src/change_detection/pipes/pipe_registry';
 import {isPresent} from 'angular2/src/facade/lang';
 import {DOM} from 'angular2/src/dom/dom_adapter';
 
-@Directive({selector: '[class]', properties: ['iterableChanges: class | keyValDiff']})
+@Directive({selector: '[class]', lifecycle: [onCheck], properties: ['rawClass: class']})
 export class CSSClass {
   _domEl;
-  constructor(ngEl: ElementRef) { this._domEl = ngEl.domElement; }
+  _pipe;
+  _prevRawClass;
+  rawClass;
+  constructor(private _pipeRegistry: PipeRegistry, ngEl: ElementRef) {
+    this._domEl = ngEl.domElement;
+  }
 
   _toggleClass(className, enabled): void {
     if (enabled) {
@@ -17,12 +22,20 @@ export class CSSClass {
     }
   }
 
-  set iterableChanges(changes) {
-    if (isPresent(changes)) {
-      changes.forEachAddedItem((record) => { this._toggleClass(record.key, record.currentValue); });
-      changes.forEachChangedItem(
+  onCheck() {
+    if (this.rawClass != this._prevRawClass) {
+      this._prevRawClass = this.rawClass;
+      this._pipe = isPresent(this.rawClass) ?
+                       this._pipeRegistry.get('keyValDiff', this.rawClass, null) :
+                       null;
+    }
+
+    if (isPresent(this._pipe) && this._pipe.check(this.rawClass)) {
+      this._pipe.forEachAddedItem(
+          (record) => { this._toggleClass(record.key, record.currentValue); });
+      this._pipe.forEachChangedItem(
           (record) => { this._toggleClass(record.key, record.currentValue); });
-      changes.forEachRemovedItem((record) => {
+      this._pipe.forEachRemovedItem((record) => {
         if (record.previousValue) {
           DOM.removeClass(this._domEl, record.key);
         }