ngModel Binding on Polymer dropdown (Angular2) - angularjs

Question

Ok so far I was successfully able to bind <paper-radio>, <paper-checkbox> with ngModel by using a Custom ControlValueAccessor for each one of them. Now I'm stuck at <paper-dropdown-menu>
Here the scenario, I can capture the paper-dropdown (iron-select) but cannot bind -two-way, i.e., using ngModel below is the HTML and custom accessor class
My form.html
<paper-dropdown-menu [(ngModel)]="mymodel.selection" label="Your Fix">
<paper-menu class="dropdown-content">
<paper-item value="1" ngDefaultControl>Coffee</paper-item>
<paper-item value="2" ngDefaultControl>Cigarettes</paper-item>
<paper-item value="3" ngDefaultControl>Chivas</paper-item></paper-menu>
</paper-dropdown-menu>
And My Custom Accessor Class
/**
* Created by pratik on 12/5/16.
*/
import {
Query,
Directive,
Renderer,
Self,
forwardRef,
Provider,
ElementRef,
QueryList
} from 'angular2/core';
import {ObservableWrapper} from 'angular2/src/facade/async';
import {NG_VALUE_ACCESSOR, ControlValueAccessor} from 'angular2/common';
import {CONST_EXPR} from 'angular2/src/facade/lang';
const SELECT_VALUE_ACCESSOR = CONST_EXPR(new Provider(
NG_VALUE_ACCESSOR, {useExisting: forwardRef(() => SelectControlValueAccessor), multi: true}));
/**
* Marks `<option>` as dynamic, so Angular can be notified when options change.
*
* ### Example
*
* ```
* <select ngControl="city">
* <option *ngFor="#c of cities" [value]="c"></option> Need to change to paper-item
* </select>
* ```
*/
#Directive({selector: 'option'}) // Tried changing to paper-item but still doesn't work
export class NgSelectOption {
}
/**
* The accessor for writing a value and listening to changes on a select element.
*/
#Directive({
selector: 'paper-dropdown-menu[ngControl],paper-dropdown-menu[ngFormControl],paper-dropdown-menu[ngModel]',
host: {
'(iron-select)': 'onChange($event.target.value)',
'(input)': 'onChange($event.target.value)',
'(blur)': 'onTouched()'
},
bindings: [SELECT_VALUE_ACCESSOR]
})
export class SelectControlValueAccessor implements ControlValueAccessor {
value: string;
onChange = (_) => {};
onTouched = () => {};
constructor(private _renderer: Renderer, private _elementRef: ElementRef,
#Query(NgSelectOption, {descendants: true}) query: QueryList<NgSelectOption>) {
this._updateValueWhenListOfOptionsChanges(query);
}
writeValue(value: any): void {
this.value = value;
this._renderer.setElementProperty(this._elementRef, 'value', value);
}
registerOnChange(fn: () => any): void { this.onChange = fn; }
registerOnTouched(fn: () => any): void { this.onTouched = fn; }
private _updateValueWhenListOfOptionsChanges(query: QueryList<NgSelectOption>) {
ObservableWrapper.subscribe(query.changes, (_) => this.writeValue(this.value));
}
}

Answer 1

Full working example. I didn't find a proper way to apply the ControlValueAccessor to <paper-dropdown-menu> but instead added it to the embeeded <paper-listbox>. The only disadvantage is that you might need a different ControlValueAccessor if you use a different content for <paper-dropdown-menu>, the advantage is that you can use the ControlValueAccessor with <paper-listbox> even when it's not wrapped in a <paper-dropdown-menu>
import {
Component,
Directive,
Renderer,
forwardRef,
Provider,
ElementRef,
ViewEncapsulation,
} from '#angular/core';
import {NG_VALUE_ACCESSOR, ControlValueAccessor} from '#angular/common';
const PAPER_MENU_VALUE_ACCESSOR = new Provider(
NG_VALUE_ACCESSOR, {useExisting: forwardRef(() => PaperMenuControlValueAccessor), multi: true});
#Directive({
selector: 'paper-listbox',
host: {'(iron-activate)': 'onChange($event.detail.selected)'},
providers: [PAPER_MENU_VALUE_ACCESSOR]
})
export class PaperMenuControlValueAccessor implements ControlValueAccessor {
onChange = (_:any) => {
};
onTouched = () => {
};
constructor(private _renderer:Renderer, private _elementRef:ElementRef) {
console.log('PaperMenuControlValueAccessor');
}
writeValue(value:any):void {
//console.log('writeValue', value);
this._renderer.setElementProperty(this._elementRef.nativeElement, 'selected', value);
}
registerOnChange(fn:(_:any) => {}):void {
this.onChange = fn;
}
registerOnTouched(fn:() => {}):void {
this.onTouched = fn;
}
}
#Component({
selector: 'my-app',
directives: [PaperMenuControlValueAccessor],
encapsulation: ViewEncapsulation.None,
template: `
<h2>Hello {{name}}</h2>
<paper-menu>
<paper-item>Item 1</paper-item>
<paper-item>Item 2</paper-item>
</paper-menu>
<paper-dropdown-menu label="Dinosaurs" >
<paper-listbox class="dropdown-content" [(ngModel)]="selected">
<paper-item *ngFor="let item of items">{{item}}</paper-item>
</paper-listbox>
</paper-dropdown-menu>
<div>selected: {{items[selected]}}</div>
`,
})
export class AppComponent {
items = ['allosaurus', 'brontosaurus', 'carcharodontosaurus', 'diplodocus'];
selected = 3;
name:string;
constructor() {
this.name = 'Angular2 (Release Candidate!)'
}
ngAfterViewInit() {
//this.selected = this.diplodocus;
}
}
Plunker example
Update
I found a similar answer for PaperDropdownMenu instead of PaperListbox Bind angular 2 model to polymer dropdown