Angular 4发出和订阅共享服务中的事件 [英] Angular 4 emitting and subscribing to an event in a shared service

问题描述

我要在我的主要组件中发出一个事件:

I am emitting an event in my main component:

main.component.ts

main.component.ts

this.sharedService.cartData.emit(this.data);

这是我的sharedService.ts

Here is my sharedService.ts

import { Component, Injectable, EventEmitter } from '@angular/core';
export class SharedService {
    cartData = new EventEmitter<any>();
} 

在我的其他(子)组件中，我想访问此值，但是以某种方式，订阅不起作用:

In my other (Sub) Component, I want to access this value, but somehow, the subscription does not work:

dashboard.ts

dashboard.ts

private myData: any;

constructor(private sharedService: SharedService) {
    this.sharedService.cartData.subscribe(
        (data: any) => myData = data,
        error => this.errorGettingData = <any>error,
        () => this.aggregateData(this.myData));
}

我错过了什么吗?当我将数据作为Injectable传递时，它工作正常. 在一些REST调用之后发生(在主组件中)发出事件.

Am I missing something? It works fine when I pass the data as an Injectable. Emitting the event (in the main component) happens after some REST calls.

更新

因此，问题在于子组件是在第一次发出事件之后创建的.我想在这种情况下，最好将数据直接注入subcompnent.

So the problem is that the Subcomponent is created after the first emit of the event. I guess in this case it is better to inject the data into the subcompnent directly.

推荐答案

更新: Plunker示例不再维护，请使用StackBlitz 这里的例子 https://stackblitz.com/edit/stackoverflow-questions-45351598-angular?file = src％2Fapp％2Fapp.component.ts

Update: Plunker example no longer maintained please use StackBlitz example here https://stackblitz.com/edit/stackoverflow-questions-45351598-angular?file=src%2Fapp%2Fapp.component.ts

我已经使用您上面提供的代码创建了一个有效的插件示例. https://plnkr.co/edit/LS1uqB?p=preview

I have created a working plunker example using the code you provided above. https://plnkr.co/edit/LS1uqB?p=preview

import { Component, NgModule, Injectable, EventEmitter, AfterViewInit } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';


@Injectable()
export class SharedService {
    cartData = new EventEmitter<any>();
} 

@Component({
  selector: 'app-app',
  template: `
    <h1>
      Main Component <button (click)="onEvent()">onEvent</button>
    </h1>
    <p>
      <app-dashboard></app-dashboard>
    </p>
  `,
})
export class App implements AfterViewInit {
  data: any = "Shared Data";

  constructor(private sharedService: SharedService) {
  }

  ngAfterViewInit() {
    this.sharedService.cartData.emit("ngAfterViewInit: " + this.data);
  }

  onEvent() {
    this.sharedService.cartData.emit("onEvent: " + this.data);
  }
}

@Component({
  selector: 'app-dashboard',
  template: `
    <h2>
      Dashboard component
    </h2>
    <p>
      {{myData}}
    </p>
  `,
})
export class AppDashboard implements AfterViewInit {
  myData: any;

  constructor(private sharedService: SharedService) {
          this.sharedService.cartData.subscribe(
          (data: any) => {
            console.log(data);
            this.myData = data;
          });
  }

}


@NgModule({
  imports: [ BrowserModule ],
  declarations: [ App, AppDashboard ],
  providers: [ SharedService ],
  bootstrap: [ App ]
})
export class AppModule {}

在此处查看生命周期挂钩 https://angular.io/guide/lifecycle-hooks

View lifecycle hooks here https://angular.io/guide/lifecycle-hooks

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