feat(radio): support radio button sharing a control

modules/@angular/forms/src/directives.ts

@@ -25,7 +25,7 @@ export {NgForm} from './directives/ng_form';
 export {NgModel} from './directives/ng_model';
 export {NgModelGroup} from './directives/ng_model_group';
 export {NumberValueAccessor} from './directives/number_value_accessor';
-export {RadioButtonState, RadioControlValueAccessor} from './directives/radio_control_value_accessor';
+export {RadioControlValueAccessor} from './directives/radio_control_value_accessor';
 export {FormControlDirective} from './directives/reactive_directives/form_control_directive';
 export {FormControlName} from './directives/reactive_directives/form_control_name';
 export {FormGroupDirective} from './directives/reactive_directives/form_group_directive';

modules/@angular/forms/src/directives/ng_form.ts

@@ -9,6 +9,7 @@ import {NG_ASYNC_VALIDATORS, NG_VALIDATORS} from '../validators';
 import {ControlContainer} from './control_container';
 import {Form} from './form_interface';
 import {NgControl} from './ng_control';
+import {NgModel} from './ng_model';
 import {NgModelGroup} from './ng_model_group';
 import {composeAsyncValidators, composeValidators, setUpControl, setUpFormGroup} from './shared';
 
@@ -107,20 +108,21 @@ export class NgForm extends ControlContainer implements Form {
 
   get controls(): {[key: string]: AbstractControl} { return this.form.controls; }
 
-  addControl(dir: NgControl): FormControl {
+  addControl(dir: NgModel): FormControl {
     const ctrl = new FormControl();
     PromiseWrapper.scheduleMicrotask(() => {
       const container = this._findContainer(dir.path);
-      setUpControl(ctrl, dir);
-      container.registerControl(dir.name, ctrl);
-      ctrl.updateValueAndValidity({emitEvent: false});
+      dir._control = <FormControl>container.registerControl(dir.name, ctrl);
+      setUpControl(dir.control, dir);
+      dir.control.updateValueAndValidity({emitEvent: false});
     });
+
     return ctrl;
   }
 
-  getControl(dir: NgControl): FormControl { return <FormControl>this.form.find(dir.path); }
+  getControl(dir: NgModel): FormControl { return <FormControl>this.form.find(dir.path); }
 
-  removeControl(dir: NgControl): void {
+  removeControl(dir: NgModel): void {
     PromiseWrapper.scheduleMicrotask(() => {
       var container = this._findContainer(dir.path);
       if (isPresent(container)) {

modules/@angular/forms/src/directives/radio_control_value_accessor.ts

@@ -36,7 +36,7 @@ export class RadioControlRegistry {
   select(accessor: RadioControlValueAccessor) {
     this._accessors.forEach((c) => {
       if (this._isSameGroup(c, accessor) && c[1] !== accessor) {
-        c[1].fireUncheck();
+        c[1].fireUncheck(accessor.value);
       }
     });
   }
@@ -48,16 +48,6 @@ export class RadioControlRegistry {
   }
 }
 
-/**
- * The value provided by the forms API for radio buttons.
- *
- * @experimental
- */
-export class RadioButtonState {
-  constructor(public checked: boolean, public value: string) {}
-}
-
-
 /**
  * The accessor for writing a radio control value and listening to changes that is used by the
  * {@link NgModel}, {@link FormControlDirective}, and {@link FormControlName} directives.
@@ -66,13 +56,12 @@ export class RadioButtonState {
  *  ```
  *  @Component({
  *    template: `
- *      <input type="radio" name="food" [(ngModel)]="foodChicken">
- *      <input type="radio" name="food" [(ngModel)]="foodFish">
+ *      <input type="radio" name="food" [(ngModel)]="food" value="chicken">
+ *      <input type="radio" name="food" [(ngModel)]="food" value="fish">
  *    `
  *  })
  *  class FoodCmp {
- *    foodChicken = new RadioButtonState(true, "chicken");
- *    foodFish = new RadioButtonState(false, "fish");
+ *    food = 'chicken';
  *  }
  *  ```
  */
@@ -85,14 +74,16 @@ export class RadioButtonState {
 export class RadioControlValueAccessor implements ControlValueAccessor,
     OnDestroy, OnInit {
   /** @internal */
-  _state: RadioButtonState;
+  _state: boolean;
   /** @internal */
   _control: NgControl;
-  @Input() name: string;
   /** @internal */
   _fn: Function;
   onChange = () => {};
-  onTouched = () => {};
+  onTouched = () => {}
+
+  @Input() name: string;
+  @Input() value: any;
 
   constructor(
       private _renderer: Renderer, private _elementRef: ElementRef,
@@ -106,21 +97,21 @@ export class RadioControlValueAccessor implements ControlValueAccessor,
   ngOnDestroy(): void { this._registry.remove(this); }
 
   writeValue(value: any): void {
-    this._state = value;
-    if (isPresent(value) && value.checked) {
-      this._renderer.setElementProperty(this._elementRef.nativeElement, 'checked', true);
+    this._state = value === this.value;
+    if (isPresent(value)) {
+      this._renderer.setElementProperty(this._elementRef.nativeElement, 'checked', this._state);
     }
   }
 
   registerOnChange(fn: (_: any) => {}): void {
     this._fn = fn;
     this.onChange = () => {
-      fn(new RadioButtonState(true, this._state.value));
+      fn(this.value);
       this._registry.select(this);
     };
   }
 
-  fireUncheck(): void { this._fn(new RadioButtonState(false, this._state.value)); }
+  fireUncheck(value: any): void { this.writeValue(value); }
 
   registerOnTouched(fn: () => {}): void { this.onTouched = fn; }
 }

modules/@angular/forms/src/forms.ts

@@ -13,7 +13,7 @@
  */
 
 
-export {FORM_DIRECTIVES, REACTIVE_FORM_DIRECTIVES, RadioButtonState} from './directives';
+export {FORM_DIRECTIVES, REACTIVE_FORM_DIRECTIVES} from './directives';
 export {AbstractControlDirective} from './directives/abstract_control_directive';
 export {CheckboxControlValueAccessor} from './directives/checkbox_value_accessor';
 export {ControlContainer} from './directives/control_container';

modules/@angular/forms/src/model.ts

@@ -282,7 +282,7 @@ export abstract class AbstractControl {
  */
 export class FormControl extends AbstractControl {
   /** @internal */
-  _onChange: Function;
+  _onChange: Function[] = [];
 
   constructor(
       value: any = null, validator: ValidatorFn|ValidatorFn[] = null,
@@ -312,7 +312,9 @@ export class FormControl extends AbstractControl {
   } = {}): void {
     emitModelToViewChange = isPresent(emitModelToViewChange) ? emitModelToViewChange : true;
     this._value = value;
-    if (isPresent(this._onChange) && emitModelToViewChange) this._onChange(this._value);
+    if (this._onChange.length && emitModelToViewChange) {
+      this._onChange.forEach((changeFn) => changeFn(this._value));
+    }
     this.updateValueAndValidity({onlySelf: onlySelf, emitEvent: emitEvent});
   }
 
@@ -329,7 +331,7 @@ export class FormControl extends AbstractControl {
   /**
    * Register a listener for change events.
    */
-  registerOnChange(fn: Function): void { this._onChange = fn; }
+  registerOnChange(fn: Function): void { this._onChange.push(fn); }
 }
 
 /**
@@ -364,9 +366,11 @@ export class FormGroup extends AbstractControl {
   /**
    * Register a control with the group's list of controls.
    */
-  registerControl(name: string, control: AbstractControl): void {
+  registerControl(name: string, control: AbstractControl): AbstractControl {
+    if (this.controls[name]) return this.controls[name];
     this.controls[name] = control;
     control.setParent(this);
+    return control;
   }
 
   /**