如何在 angular 中创建和触发自定义事件

Question

I'm new in Angular and I've read about event binding so I can do something like this:

<button (click)="doSomething()"></button>

I'd like to know if it's possible to create a custom event and do the same thing. Let's say that I want to have a custom event like: deleteItem , is it possible to do something like this? And how?

<my-component (deleteItem)="doSomething()"></my-component>

Answer 1

Of course, you can use an eventEmitter in my-component ts file add this

 @Output() deleteItem= new EventEmitter();

and when you want to rise the event do this

  this.deleteItem.emit();

also you can pass data like this

  this.countUpdate.emit({value: some data });

then catch it in the parent component like this

<my-component (deleteItem)="doSomething($event)"></my-component>

and in the parent ts file

    doSomething(event)
    { 
       console.log(event);
    }

Answer 2

You should check out Angular's documentations example for parent listens to child event :

You declare a class property with the @Output() decorator and instantiate it to a new EventEmitter instance.

Example from the Angular docs

import { Component, EventEmitter, Input, Output } from '@angular/core';

@Component({
  selector: 'app-voter',
  template: `
    <h4>{{name}}</h4>
    <button (click)="vote(true)"  [disabled]="didVote">Agree</button>
    <button (click)="vote(false)" [disabled]="didVote">Disagree</button>
  `
})
export class VoterComponent {
  @Input()  name: string;
  @Output() voted = new EventEmitter<boolean>();
  didVote = false;

  vote(agreed: boolean) {
    this.voted.emit(agreed);
    this.didVote = true;
  }
}

Remember it is good practice to always add generic typing to the EventEmitter if it emits a value.

If an event emits a boolean value you should instantiate it with @Output() eventName = new EventEmitter<boolean>();

The component above could be used in a parent component with <app-voter (voted)="handleVote($event)"></app-voter>

Answer 3

EventEmitter 可以用来创建你自己的自定义事件，eventemitter 是 angular 框架中的对象。

@Output() deleteItem= new EventEmitter<{itemName:string}>(); ItemName=''; this.deleteItem.emit({ItemName=this.itemName});

Answer 4

@Output() loaderStatus= new EventEmitter<{Status:boolean}>(); Status=true; 
this.loaderEvent.emit({Status=false});