feat(form): implemented an imperative way of updating the view by updating the value of a control

modules/angular2/src/forms/directives/form_control_directive.ts

@@ -1,4 +1,5 @@
 import {CONST_EXPR} from 'angular2/src/facade/lang';
+import {StringMapWrapper} from 'angular2/src/facade/collection';
 import {EventEmitter, ObservableWrapper} from 'angular2/src/facade/async';
 
 import {Directive, Ancestor, onChange} from 'angular2/angular2';
@@ -53,20 +54,24 @@ const formControlBinding =
 export class FormControlDirective extends ControlDirective {
   control: Control;
   ngModel: EventEmitter;
+  _added: boolean;
+  model: any;
 
   constructor() {
     super();
     this.ngModel = new EventEmitter();
+    this._added = false;
   }
 
-  onChange(_) {
-    setUpControl(this.control, this);
-    this.control.updateValidity();
-  }
-
-  set model(value) {
-    this.control.updateValue(value);
-    this.valueAccessor.writeValue(value);
+  onChange(c) {
+    if (!this._added) {
+      setUpControl(this.control, this);
+      this.control.updateValidity();
+      this._added = true;
+    }
+    if (StringMapWrapper.contains(c, "model")) {
+      this.control.updateValue(this.model);
+    }
   }
 
   viewToModelUpdate(newValue: any): void { ObservableWrapper.callNext(this.ngModel, newValue); }

modules/angular2/src/forms/directives/form_model_directive.ts

@@ -89,8 +89,7 @@ export class FormModelDirective extends ControlContainerDirective implements For
 
   updateModel(dir: ControlDirective, value: any): void {
     var c  = <Control>this.form.find(dir.path);
-    c.value = value;
-    dir.valueAccessor.writeValue(value);
+    c.updateValue(value);
   }
 
   _updateDomValue() {

modules/angular2/src/forms/directives/ng_model_directive.ts

@@ -40,8 +40,7 @@ export class NgModelDirective extends ControlDirective {
     };
 
     if (StringMapWrapper.contains(c, "model")) {
-      this.control.value = this.model;
-      this.valueAccessor.writeValue(this.model);
+      this.control.updateValue(this.model);
     }
   }
 

modules/angular2/src/forms/directives/shared.ts

@@ -18,10 +18,15 @@ export function setUpControl(c: Control, dir: ControlDirective) {
 
   c.validator = Validators.compose([c.validator, dir.validator]);
   dir.valueAccessor.writeValue(c.value);
+
+  // view -> model
   dir.valueAccessor.registerOnChange(newValue => {
     dir.viewToModelUpdate(newValue);
     c.updateValue(newValue);
   });
+
+  // model -> view
+  c.registerOnChange(newValue => dir.valueAccessor.writeValue(newValue));
 }
 
 function _throwError(dir: ControlDirective, message: string): void {

modules/angular2/src/forms/directives/template_driven_form_directive.ts

@@ -65,8 +65,7 @@ export class TemplateDrivenFormDirective extends ControlContainerDirective imple
   updateModel(dir: ControlDirective, value: any): void {
     this._later(_ => {
       var c = <Control>this.form.find(dir.path);
-      c.value = value;
-      dir.valueAccessor.writeValue(value);
+      c.updateValue(value);
     });
   }