浅析Angular19 自定义表单控件(2)

日期：2020-05-11 栏目：程序人生浏览：次

HTML

import { Component, OnInit } from '@angular/core';
import { ControlValueAccessor } from '@angular/forms';
@Component({
 selector: 'app-counter',
 templateUrl: './counter.component.html',
 styleUrls: ['./counter.component.scss']
})
export class CounterComponent implements OnInit {
 countNumber: number = 0;
 constructor() { }
 ngOnInit() {
 }
 onIncrease() {
 this.countNumber++;
 }
 onDecrease() {
 this.countNumber--;
 }
}

3.1.1 功能描述

点击增加按钮时当前计数会增加1，点击减少按钮时当前计数会剪1

3.1.2 直接在其他组件中使用时会报错

报错信息如下：

错误信息是说我们我们使用的组件<app-counter>还不是一个表单控件

3.2 如何让<app-counter>组件变成一个表单控件组件

3.2.1 实现 ControlValueAccessor 接口

export class CounterComponent implements OnInit, ControlValueAccessor {
 countNumber: number = 0;
 constructor() { }
 ngOnInit() {
 }
 onIncrease() {
 this.countNumber++;
 }
 onDecrease() {
 this.countNumber--;
 }
 /**将数据从模型传输到视图 */
 writeValue(obj: any): void {
 }
 /**将数据从视图传播到模型 */
 registerOnChange(fn: any): void {
 }
 registerOnTouched(fn: any): void {
 }
 setDisabledState?(isDisabled: boolean): void {
 }
}

3.2.2 指定依赖信息providers

import { Component, OnInit, forwardRef } from '@angular/core';
import { ControlValueAccessor, NG_VALUE_ACCESSOR } from '@angular/forms';
@Component({
 selector: 'app-counter',
 templateUrl: './counter.component.html',
 styleUrls: ['./counter.component.scss'],
 providers: [
 {
  provide: NG_VALUE_ACCESSOR,
  useExisting: forwardRef(() => CounterComponent),
  multi: true
 }
 ]
})
export class CounterComponent implements OnInit, ControlValueAccessor {
 countNumber: number = 0;
 constructor() { }
 ngOnInit() {
 }
 onIncrease() {
 this.countNumber++;
 }
 onDecrease() {
 this.countNumber--;
 }
 /**将数据从模型传输到视图 */
 writeValue(obj: any): void {
 }
 /**将数据从视图传播到模型 */
 registerOnChange(fn: any): void {
 }
 registerOnTouched(fn: any): void {
 }
 setDisabledState?(isDisabled: boolean): void {
 }
}

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浅析Angular19 自定义表单控件(2)

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