Angular 2单例服务不作为单身人士

所以我有一个名为TargetService的服务,它注入了各种其他组件.此TargetService有一个名为Targets的属性,它是Target对象的集合.

我的问题是我希望这个集合在路由到另一个视图后仍然存在.我的路由工作正常,但是一旦路由发生变化,服务就会丢失任何变量的内容,基本上,它会重新初始化服务.我的理解是这些注入的服务是可以传递的单身人士？

在下面的示例中,在TargetIndex上,单击一个按钮,该按钮填充服务上的Targets []对象(this.targetService.targets = ts;).工作正常,然后我路由到TargetShow页面,然后回到这个索引,现在这个Targets []属性是空的,当我希望它包含我已经填充的.

我在这里想念的是什么？

App.Module

const routes: Routes = [
  { path: '',redirectTo: 'targets',pathMatch: 'full'},{ path: 'targets',component: TargetIndexComponent },{ path: 'targets/:id',component: TargetShowComponent }
]

@NgModule({
  declarations: [
    AppComponent,TargetComponent,TargetIndexComponent,TargetShowComponent
  ],imports: [
    browserModule,FormsModule,ReactiveFormsModule,HttpModule,RouterModule.forRoot(routes)
  ],providers: [TargetService],bootstrap: [AppComponent]
})
export class AppModule { }

TargetService

@Injectable()
export class TargetService {
  public targets: Target[];

  constructor(private http: Http) {}

  getTargets(hostname: String): Observable<Target[]> {
    return this.http.request(`url`).map(this.extractData);
  }

  private extractData(res: Response) {
    let body = res.json();
    return body || [];
  }

}

TargetIndex

@Component({
  selector: 'app-targets',templateUrl: './target-index.component.html',styleUrls: ['./target-index.component.css'],providers: [TargetService]
})
export class TargetIndexComponent implements OnInit {
  loading = false;

  constructor(private http: Http,private targetService: TargetService) {}

  loadTargets(hostname: HTMLInputElement) {
    this.loading = true;
    this.targetService.getTargets(hostname.value)
    .subscribe((ts: Target[]) => {
      this.targetService.targets = ts;
      this.loading = false;
    })
  }

  ngOnInit() {
  }

}

TargetShow

@Component({
  selector: 'app-target-show',templateUrl: './target-show.component.html',styleUrls: ['./target-show.component.css'],providers: [TargetService]
})
export class TargetShowComponent implements OnInit {
  id: string

  constructor(private route: ActivatedRoute,private targetService: TargetService) {
    route.params.subscribe(params => { this.id = params['id']; })
  }

  ngOnInit() {
  }

}

尝试从组件提供程序中删除TargetService,因为您已将其添加到模块提供程序中.将此服务添加到组件提供程序时,DI会创建它的新实例.

这是https://angular.io/docs/ts/latest/guide/dependency-injection.html的引用：

When to use the NgModule and when an application component? On the one hand,a provider in an NgModule is registered in the root
injector. That means that every provider registered within an NgModule
will be accessible in the entire application.

On the other hand,a provider registered in an application component is available only on that component and all its children.

原文地址：https://www.jb51.cc/angularjs/142195.html

Angular 2单例服务不作为单身人士

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