来自导出类的公共方法的返回类型具有或正在使用名称＆＃39;订阅＆＃39;来自外部模块

Question

我在以下代码中遇到错误，并且我想知道哪些操作不正确。我试图从REST API中获取数据并收到此错误。

代码：

    import {Injectable} from "@angular/core";
    //import {POSTS} from "./mock-posts";
    import { Http, Headers,RequestOptions } from '@angular/http';
    import 'rxjs/add/operator/map';

    @Injectable()
    export class PostService {
      posts: any;

      // API LINK
      GET_ALL_POST : string = 'http://xxx.xxx/get_all_posts';

      constructor(public http: Http) {
        this.http = http;
      }


       getAll() {
        return this.http
          .get(this.GET_ALL_POST)
          .map(res => res.json());
      }
    }

错误：

    [02:36:20]  Error: Error at C:/Users/nonren/Documents/Ionic/socialtag/.tmp/services/post-service.ts:18:3
    [02:36:20]  Return type of public method from exported class has or is using name 'Observable' from external module
        "C:/Users/nonren/Documents/Ionic/socialtag/node_modules/rxjs/Observable" but cannot be named.
    [02:36:20]  ngc failed
    [02:36:20]  ionic-app-script task: "build"
    [02:36:20]  Error: Error

上述错误的屏幕截图：

代码I用于致电getAll()：

    import {Component} from '@angular/core';
    import {NavController} from 'ionic-angular';
    import {PostService} from '../../services/post-service';
    import {PostPage} from '../post/post';
    import {UserPage} from '../user/user';

    @Component({
      selector: 'page-home',
      templateUrl: 'home.html'
    })
    export class HomePage {
      public posts: any;

      constructor(public nav: NavController, public postService: PostService) {
        this.posts = postService.getAll();postService.getAll().subscribe(
      data => {
        this.posts = data;
        console.log(this.posts);
      }
    );
    }

Answer 1

您无法订阅Observable两次。

如果您希望进行异步调用的方法的调用者能够订阅结果，则需要确保返回Observable，但如果此方法调用subscribe()，则而是返回Subscription。

将方法更改为使用.map()而不是subscribe()。然后它将返回Observable。

getServerData() {
  return this.http.get(...).map(response => response.json()));
}

otherMethod() {
  this.service.getServiceData().subscribe(response => this.data = response);
}