Angular Reactive Form 的一个具体使用例子

在 module 实现里，务必导入下列 module：

import { ReactiveFormsModule } from '@angular/forms';

template 实现代码：

<input type="text" [formControl]="jerryFormControl">
<div>{{ response }}</div>

其中 formControl Directive，绑定的是 FormControl 具体实例。Component 完整的实现代码：

import { Component, OnInit } from '@angular/core';
import { FormControl } from '@angular/forms';
import { HttpClient} from '@angular/common/http';
import { throttleTime } from "rxjs/operators";

// this endpoint is implemented in https://github.com/wangzixi-diablo/ui5-toolset, local.js

const APIENDPOINT = "http://localhost:3000/echo?data=";

@Component({
  selector: 'jerryform',
  templateUrl: './react-form.component.html'
})
export class JerryReactFormComponent implements OnInit  {
  constructor(private http:HttpClient){}

  response = '';

  onValueChanged = (value)=>{
    console.log('new value from live change: ' + value);
    
    const url = `${APIENDPOINT}${value}`;
    
    const options = {
      responseType: 'text' as 'json'
    }

    var $http = this.http.get(url, options);
    $http.subscribe(
      (response:string)=>{
        console.log('response from http: ' + response);
        this.response = response},
      (error)=>console.log('error: ' + error));
  }

  ngOnInit(): void {

    // this.jerryFormControl.valueChanges.pipe(debounceTime(3000)).subscribe(this.onValueChanged);

    this.jerryFormControl.valueChanges.pipe(throttleTime(2000)).subscribe(this.onValueChanged);
  }
  jerryFormControl = new FormControl('');
}

在 Component 的实现代码里，我们并不会直接操作 template 里的 input 标签，而是通过其绑定的 formControl 实例 jerryFormControl 暴露出的 valueChanges Observable，来注册我们应用程序自己的逻辑，即事件响应函数 onValueChanged.