Angular 4发布和订阅共享服务中的事件

Question

我在我的主要组件中发出了一个事件:

main.component.ts

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

这是我的sharedService.ts

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

在我的其他(Sub)组件中,我想访问此值,但不知何故,订阅不起作用:

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调用之后发生事件(在主组件中).

更新

所以问题是在第一次发射事件之后创建了子组件.我想在这种情况下最好直接将数据注入subcompnent.

Answer 1

更新: 不再维护Plunker示例请在此处使用StackBlitz示例 https://stackblitz.com/edit/stackoverflow-questions-45351598-angular?file=src%2Fapp%2Fapp.component.ts

我使用您在上面提供的代码创建了一个有效的plunker示例.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 {}

查看生命周期钩子https://angular.io/guide/lifecycle-hooks