如何编写一个完整的Angular4 FormText 组件

import { Component, Output, Input, forwardRef, EventEmitter} from '@angular/core';
import {ControlValueAccessor, NG_VALUE_ACCESSOR} from '@angular/forms';

@Component({
 selector: 'form-text',
 template: `
 <div >
 <label>{{label}}：</label>
 <input type="text" [(ngModel)]="value"
 placeholder="{{placeholder}}" >
 </div>
 `,
 providers: [
 {
 provide:NG_VALUE_ACCESSOR,
 useExisting:forwardRef(()=>FormTextComponent),
 multi:true
 }
 ]
})
export class FormTextComponent implements ControlValueAccessor {
 
 @Input() label:string = '';
 @Input() placeholder: string='';

 @Output() onChange: EventEmitter<any> = new EventEmitter<any>();
 
 public innerValue: any;
 public changeFn: Function = () => {};
 

 get value(): any {
 return this.innerValue;
 };

 set value(v: any) {
 if (v !== this.innerValue) {
 this.innerValue = v;
 this.changeFn(v);
 }
 }


 writeValue(value: any) {
 if (value !== this.innerValue) {
 this.innerValue = value;
 }
 }

 registerOnChange(fn: any) {
 this.changeFn = fn;
 }

 registerOnTouched(fn: any) {
 //
 }

}

<form-text [(ngModel)]="mobile" [placeholder]="placeholder" [label]="label"></form-text>
<p>{{mobile}}</p>