如何使用formcomtrol捕获选择元素的绑定事件-ReactiveFomrModule -Angular 4 [英] How to capture bind event of select element using formcomtrol - ReactiveFomrModule -Angular 4

问题描述

我正在使用reactformmodule，并为select标签创建了一个formcontrol.在页面加载时，我正在从后端获取数据，并使用patchvalue将其绑定到selectformcontrol.但是这样做时，不会触发select的change事件.

I am using reactiveformmodule and has created a formcontrol for select tag. On load of the page I am fetching data from backend and binding it using patchvalue to the selectformcontrol. But in doing this the change event of select is not fired.

 in .html
 <select id="businessType" formControlName="businessType">
                    <option value="-1">Business type</option>
                    <option *ngFor="let business of businessTypes; let i=index;" [value]="i">{{business.b_type}}</option>
                </select>

 in .ts
 this.formGroupObject.patchValue({
        'businessType': 0 //"0" is coming from backend
    })

我的应用程序中有很多选择标签，因此无法捕获每个selectform控件的值更改.

I have lot of select tags across my application, so cannot capture valuechange for each selectformcontrol.

我想通过创建一个指令并向其添加hostlistener来概括如下

I wanted to generalize by creating a directive and adding hostlistener to it like below

@Directive({
selector: 'select',
})

和我在课堂上的代码

@HostListener('change', ['$event'])
onChange(event) {
    //do something
}

但是当使用表单控件.patchValue修补数据时，不会触发此onChange，当我手动选择该选项时，将触发此onChange.

But this onChange is not fired when data is patched using form control .patchValue, when I manually select option then this is triggered.

我想捕获一个事件，该事件在选择标记中修补数据时触发.

I want to capture an event which gets triggered when the data is patched in select tag.

推荐答案

因此，分享一些示例代码以满足您的要求，这些示例对我有用:

So sharing some sample code to meet your requirement which worked for me :

指令

 import { Directive, ElementRef, HostListener } from '@angular/core';

    @Directive({
        selector: 'select'
    })
    export class SelectDirective {
        constructor(private el: ElementRef) { 
        }

        @HostListener('change', ['$event'])
        onChange(event) {
            console.log(event);
        }

        @HostListener('ngModelChange') onNgModelChange() {
            console.log('ngModelChange');
        }

    }

模块(要在其中使用)

declarations: [
    SelectDirective
  ]

这篇关于如何使用formcomtrol捕获选择元素的绑定事件-ReactiveFomrModule -Angular 4的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！