Angular 2 - Using Shared Service

2020-01-25 10:34发布

问题:

Looks like shared services is the best practice to solve many situations such as communication among components or as replacement of the old $rootscope concept of angular 1. I'm trying to create mine, but it's not working. Any help ? ty !!!

app.component.ts

import {Component} from 'angular2/core';
import {OtherComponent} from './other.component';
import {SharedService} from './services/shared.service';
@Component({
selector: 'my-app',
providers: [SharedService],
directives: [OtherComponent],
template: `
    <button (click)="setSharedValue()">Add value to Shared Service</button>
    <br><br>
    <other></other>
`
})
export class AppComponent { 
data: string = 'Testing data';
setSharedValue(){
    this._sharedService.insertData(this.data);
    this.data = '';
    console.log('Data sent');
}
constructor(private _sharedService: SharedService){}
}

other.component.ts

import {Component, OnInit} from "angular2/core";
import {SharedService} from './services/shared.service';
@Component({
selector : "other",
providers : [SharedService],
template : `
I'm the other component. The shared data is: {{data}}
`,
})
export class OtherComponent implements OnInit{
data: string[] = [];
constructor(private _sharedService: SharedService){}
ngOnInit():any {
    this.data = this._sharedService.dataArray;
}
}

回答1:

Most of time, you need to define your shared service when bootstrapping your application:

bootstrap(AppComponent, [ SharedService ]);

and not defining it again within the providers attribute of your components. This way you will have a single instance of the service for the whole application.


In your case, since OtherComponent is a sub component of your AppComponent one, simply remove the providers attribute like this:

@Component({
  selector : "other",
  // providers : [SharedService], <----
  template : `
    I'm the other component. The shared data is: {{data}}
  `,
})
export class OtherComponent implements OnInit{
  (...)
}

This way they will shared the same instance of the service for both components. OtherComponent will use the one from the parent component (AppComponent).

This is because of the "hierarchical injectors" feature of Angular2. For more details, see this question:

  • What's the best way to inject one service into another in angular 2 (Beta)?


回答2:

You need to add a global provider in your module, then you dont need to add this provider in each component. try this

app.module.ts

@NgModule({
    imports: [BrowserModule, FormsModule, HttpModule],
    declarations: [AppComponent, LoginComponent, InComponent],
    providers: [LoginService],
    bootstrap: [AppComponent]
})

app.component.ts

@Component({
    moduleId: module.id,
    selector: 'app',
    templateUrl: './app.component.html'
})
export class AppComponent {
    constructor(public loginService: LoginService) {

    }
}

login.component.ts

@Component({
    moduleId: module.id,
    selector: 'login',
    templateUrl: './login.component.html'
})
export class LoginComponent {

    constructor(public loginService: LoginService) {

    }
}

I hope this work for you.