从Angular2服务返回一个空的Observable

Question

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();
    }
}

这项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.此解析程序包含以下逻辑:

/* ========== 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,当我浏览时/applications,我遇到了一个错误Uncaught (in promise): Error: no elements in sequence..

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.如何解决这个问题.

亲切的问候,

Answer 1

替换Observable.empty()为Observable.of([]).ofover 的偏好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:

Observable.empty()

创建一个Observable,它不会向Observer发送任何项目,并立即发出完整的通知.

Observable.of()

创建一个Observable,它会一个接一个地发出您指定为参数的某些值,然后发出完整的通知.