当有角度的 *ngIf 语句在模板中求值时触发的事件 [英] Event to fire when an angular *ngIf statement evaluates in template

问题描述

如果我有以下几点:

<p>{{user.name}}</p>

当上面的 div 最终出现在屏幕上时，我是否可以执行代码?

解决方案

*ngIf 将删除该 DOM 元素和所有附加的组件/指令.因此，您可以编写一个简单的指令，在首次创建事件时执行该事件.当 *ngIf 从 false 转换为 true 指令将被创建(一次又一次，等等...)

@Directive({selector: '[after-if]'})导出类 AfterIfDirective 实现 AfterContentInit {@Output('after-if')公开之后:EventEmitter= new EventEmitter();公共 ngAfterContentInit(): 无效 {//超时有助于防止意外更改错误setTimeout(()=> this.after.next());}}

示例 HTML:

<div *ngIf="user$ | async as user" (after-if)="你的表达式"><p>{{user.name}}</p>

If I have the following:

<div *ngIf="user$ | async as user" class="container">
   <p>{{user.name}}</p>
</div>

Is there a way I can execute code when the div above finally appears on screen?

解决方案

The *ngIf will remove that DOM element and all attached components/directives. So you can just write a simple directive that executes an event when it's first created. When the *ngIf transitions from false to true the directive will be created (again, and again, etc...)

@Directive({selector: '[after-if]'})
export class AfterIfDirective implements AfterContentInit {
    @Output('after-if')
    public after: EventEmitter<void> = new EventEmitter<void>();

    public ngAfterContentInit(): void {
       // timeout helps prevent unexpected change errors
       setTimeout(()=> this.after.next());
    }
}

Sample HTML:

<div *ngIf="user$ | async as user" (after-if)="your expression">
   <p>{{user.name}}</p>
</div>

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