refactor(change_detection): removed NO_CHANGED and replaced it with WrappedValue

modules/angular2/src/change_detection/pipes/async_pipe.js

@@ -1,6 +1,6 @@
 import {Observable, ObservableWrapper} from 'angular2/src/facade/async';
 import {isBlank, isPresent} from 'angular2/src/facade/lang';
-import {Pipe, NO_CHANGE} from './pipe';
+import {Pipe, WrappedValue} from './pipe';
 import {ChangeDetectorRef} from '../change_detector_ref';
 
 /**
@@ -67,10 +67,10 @@ export class AsyncPipe extends Pipe {
     }
 
     if (this._latestValue === this._latestReturnedValue) {
-      return NO_CHANGE;
+      return this._latestReturnedValue;
     } else {
       this._latestReturnedValue = this._latestValue;
-      return this._latestValue;
+      return WrappedValue.wrap(this._latestValue);
     }
   }
 

modules/angular2/src/change_detection/pipes/iterable_changes.js

@@ -14,7 +14,7 @@ import {
   looseIdentical,
 } from 'angular2/src/facade/lang';
 
-import {NO_CHANGE, Pipe} from './pipe';
+import {WrappedValue, Pipe} from './pipe';
 
 export class IterableChangesFactory {
   supports(obj):boolean {
@@ -117,9 +117,9 @@ export class IterableChanges extends Pipe {
 
   transform(collection){
     if (this.check(collection)) {
-      return this;
+      return WrappedValue.wrap(this);
     } else {
-      return NO_CHANGE;
+      return this;
     }
   }
 

modules/angular2/src/change_detection/pipes/keyvalue_changes.js

@@ -1,7 +1,7 @@
 import {ListWrapper, MapWrapper, StringMapWrapper} from 'angular2/src/facade/collection';
 import {stringify, looseIdentical, isJsObject} from 'angular2/src/facade/lang';
 
-import {NO_CHANGE, Pipe} from './pipe';
+import {WrappedValue, Pipe} from './pipe';
 
 /**
  * @exportedAs angular2/pipes
@@ -54,9 +54,9 @@ export class KeyValueChanges extends Pipe {
 
   transform(map){
     if (this.check(map)) {
-      return this;
+      return WrappedValue.wrap(this);
     } else {
-      return NO_CHANGE;
+      return this;
     }
   }
 

modules/angular2/src/change_detection/pipes/null_pipe.js

@@ -1,5 +1,5 @@
 import {isBlank} from 'angular2/src/facade/lang';
-import {Pipe, NO_CHANGE} from './pipe';
+import {Pipe, WrappedValue} from './pipe';
 
 /**
  * @exportedAs angular2/pipes
@@ -35,9 +35,9 @@ export class NullPipe extends Pipe {
   transform(value) {
     if (! this.called) {
       this.called = true;
-      return null;
+      return WrappedValue.wrap(null);
     } else {
-      return NO_CHANGE;
+      return null;
     }
   }
 }

modules/angular2/src/change_detection/pipes/pipe.js

@@ -1,13 +1,33 @@
 /**
- * Indicates that the result of a {@link Pipe} transformation has not changed since the last time the pipe was called.
+ * Indicates that the result of a {@link Pipe} transformation has changed even though the reference has not changed.
  *
- * Suppose we have a pipe that computes changes in an array by performing a simple diff operation. If
- * we call this pipe with the same array twice, it will return `NO_CHANGE` the second time.
+ * The wrapped value will be unwrapped by change detection, and the unwrapped value will be stored.
  *
  * @exportedAs angular2/pipes
  */
+export class WrappedValue {
+  wrapped:any;
 
-export var NO_CHANGE = new Object();
+  constructor(wrapped:any) {
+    this.wrapped = wrapped;
+  }
+
+  static wrap(value:any):WrappedValue {
+    var w = _wrappedValues[_wrappedIndex++ % 5];
+    w.wrapped = value;
+    return w;
+  }
+}
+
+var _wrappedValues = [
+  new WrappedValue(null),
+  new WrappedValue(null),
+  new WrappedValue(null),
+  new WrappedValue(null),
+  new WrappedValue(null)
+];
+
+var _wrappedIndex = 0;
 
 /**
  * An interface for extending the list of pipes known to Angular.