从Angular2服务返回一个空的Observable
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我正在构建一个Angular 2应用程序,它使用服务来收集数据.
该服务确实包含以下逻辑: /* ========== CORE COMPONENTS ========== */
import { Injectable } from '@angular/core';
import { Http,Response } from '@angular/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/Rx';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/catch';
/* ========== MODELS ========== */
import { IApplicationViewModel } from './models/application.model';
/* ========== CONSTANTS ========== */
import { LogzillaServerConfiguration } from '../../app.configuration';
@Injectable()
export class ApplicationService {
private getAllEndpoint = LogzillaServerConfiguration.host + '/api/administration/application/getAll';
// Initializes a new instance of the 'ApplicationService'.
constructor(private http: Http) { }
// Get all the 'logzilla' applications.
getApplications(): Observable<IApplicationViewModel[]> {
return this.http.get(this.getAllEndpoint)
.map((response: Response) => <IApplicationViewModel[]>response.json().model)
.catch(this.handleError);
}
// Handle an error that occured while retrieving the data.
// This method will throw an error to the calling code.
private handleError(error: Response) {
return Observable.empty();
}
}
该服务的作用是从端点检索数据,并将其映射到模型,当发生错误时,我返回一个空的Observable. 我还有一个解析器,用于在更改活动路由之前从服务加载数据. /* ========== CORE COMPONENTS ========== */
import { Injectable } from '@angular/core';
import { Resolve,ActivatedRouteSnapshot } from '@angular/router';
/* ========== APPLICATION SERVICES ========== */
import { ApplicationService } from './application.service';
/* ========== MODELS ========== */
import { IApplicationViewModel } from './models/application.model';
import { IApplicationLogLevel } from './models/applicationLevel.model';
// Defines the 'resolver' which is used to resolve the applications.
@Injectable()
export class ApplicationResolver implements Resolve<IApplicationViewModel[]> {
// Initializes a new instance of the 'ApplicationResolver'.
constructor(private applicationService: ApplicationService) { }
// Get all the registered applications.
resolve(route: ActivatedRouteSnapshot) {
return this.applicationService.getApplications();
}
}
我的路线的定义是: { path: 'applications',component: ApplicationComponent,pathMatch: 'full',resolve: {
application: ApplicationResolver
}},
但是,当我浏览到/ applications时,我遇到了一个错误Uncaught(在promise中):错误:序列中没有元素.. 编辑:添加组件 @Component({
selector: 'logzilla-applications',templateUrl: './src/app/pages/applications/application.template.html'
})
@Injectable()
export class ApplicationComponent implements OnInit {
hasApplications: boolean;
applications: IApplicationViewModel[];
errorMessage: string;
// Initializes a new instance of the 'ApplicationComponent'.
constructor (private route: ActivatedRoute) {
console.log('I am here.');
}
// This method is executed when the component is loaded.
ngOnInit() {
}
我的组件的构造函数不是调用的事件. 亲切的问候,
用Observable.of([])替换Observable.empty(). over empty for the empty是官方Angular
Tour of Heroes教程用来返回空的observable,并且是我在所有应用程序中使用的内容.
它们之间的区别似乎是返回任何内容,还是空数组. 来自官方rxjs文档:
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