如何使用共享服务将数据从一个组件发送到另一个组件 [英] How to send data from one component to another using a shared service

问题描述

我想使用主题将数据发送到另一个组件(出于盈利目的).我无法取回数据.这是我的代码:

I wanted to send data using subject to another component (for a earning purpose). I am not able to fetch back the data. Here is my code:

app.component.ts

import { Component } from '@angular/core';
import { shareService } from './share.service';

@Component({
 selector: 'my-app',
  template: `
  <hello></hello>
  <button (click)="passData()">
    Start
  </button>
  `,
  styleUrls: [ './app.component.css' ],
  providers:[shareService]
})
export class AppComponent  {
  constructor(private service : shareService){}

  passData(){
   this.service.send("hello");
}

}

hello.component.ts

import { Component, Input } from '@angular/core';
import { shareService } from './share.service';
import { Subscription }   from 'rxjs/Subscription';

@Component({
  selector: 'hello',
  template: `<h1>Hello!</h1>`,
  styles: [`h1 { font-family: Lato; }`],
  providers:[shareService]
})
export class HelloComponent  {
  subscription: Subscription;
    constructor(private share : shareService){
    this.subscription =  share.subj$.subscribe(val=>{
    console.log(val);
    })
  }
}

share.service.ts

import { Injectable } from '@angular/core';
import { Subject }    from 'rxjs/Subject';

@Injectable()
export class shareService{

  private sub = new Subject();
  subj$ = this.sub.asObservable();

    send(value: string) {
    this.sub.next(value);
  }

}

我没有在控制台中获取值.

I am not getting the value in console.

这是工作演示:DEMO

推荐答案

通过放置:

@Component({
  .....
  providers: [sharedService]
})

在这两个组件中，您都在创建共享服务的两个不同实例.每个实例并不知道"来自每个组件的数据.在模块级别提供它并创建一个单例服务:

in both components, you are creating two distinct instances of the shared service. Each instance is not 'aware' of the data from each component. Provide it at module level and create a singleton service:

@NgModule({
  ....
  providers: [sharedService]
})

通过这种方式，您可以将服务作为单个实例注入到两个组件中，这样它们就可以像共享数据一样共享它.

This way, you inject the service as a single instance in the both components, so they can share it as they will share the data.

或者使用 Angular 的首选新方式:

从 Angular 6.0 开始，创建单例的首选方式service 是在服务中指定它应该在应用程序根.这是通过将 providedIn 设置为 root 来完成的服务的@Injectable 装饰器:

Beginning with Angular 6.0, the preferred way to create a singleton service is to specify on the service that it should be provided in the application root. This is done by setting providedIn to root on the service's @Injectable decorator:

@Injectable({
  providedIn: 'root',
})

演示

参见另见

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