What are the steps required to implement a complete Angular4 FormText component?

This time I will bring you the steps required to implement a complete Angular4 FormText component, and what are the precautions to implement a complete Angular4 FormText component. The following is a practical case, let's take a look.

This article mainly introduces how to write a complete Angular4 FormText component, share it with everyone, and leave a note for yourself

Component definition

import { Component, Output, Input, forwardRef, EventEmitter} from '@angular/core';
import {ControlValueAccessor, NG_VALUE_ACCESSOR} from '@angular/forms';
@Component({
 selector: 'form-text',
 template: `
  <p >
    <label>{{label}}：</label>
    <input type="text" [(ngModel)]="value"
    placeholder="{{placeholder}}" >
  </p>
 `,
 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) {
  //
 }
}

Component usage

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

Points to note:

Need to configure the providers of the component
Need to implement ControlValueAccessorInterface                                                            

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

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