Input 是属性装饰器,用来定义组件内的输入属性。在实际应用场合,我们主要用来实现父组件向子组件传递数据。Angular 应用是由各式各样的组件组成,当应用启动时,Angular 会从根组件开始启动,并解析整棵组件树,数据由上而下流下下一级子组件。
子组件counter.component.ts
import { Component, Input } from '@angular/core';
@Component({
selector: 'exe-counter',
template: `
<p>当前值: {{ count }}</p>
<button (click)="increment()"> + </button>
<button (click)="decrement()"> - </button>
`
})
export class CounterComponent {
@Input() count: number = 0;
increment() {
this.count++;
}
decrement() {
this.count--;
}
}
父组件app.component.ts
import { Component } from '@angular/core';
@Component({
selector: 'exe-app',
template: `
<exe-counter [count]="initialCount"></exe-counter>
`
})
export class AppComponent {
initialCount: number = 5;
}
子组件counter.component.ts
import { Component, Input, Output, EventEmitter } from '@angular/core';
@Component({
selector: 'exe-counter',
template: `
<p>当前值: {{ count }}</p>
<button (click)="increment()"> + </button>
<button (click)="decrement()"> - </button>
`
})
export class CounterComponent {
@Input() count: number = 0;
@Output() change: EventEmitter<number> = new EventEmitter<number>();
increment() {
this.count++;
this.change.emit(this.count);
}
decrement() {
this.count--;
this.change.emit(this.count);
}
}
父组件app.component.ts
import { Component } from '@angular/core';
@Component({
selector: 'exe-app',
template: `
<p>{{changeMsg}}</p>
<exe-counter [count]="initialCount"
(change)="countChange($event)"></exe-counter>
`
})
export class AppComponent {
initialCount: number = 5;
changeMsg: string;
countChange(event: number) {
this.changeMsg = `子组件change事件已触发,当前值是: ${event}`;
}
}