无法解析所有参数 [英] Can't resolve all parameters

问题描述

我尝试在我的组件中注入服务，但出现此错误:

I try to inject service in my component and I get this error:

news.component.ts

import { Component,OnInit } from '@angular/core';
import { NewsService } from './index';


declare var jQuery:any;

@Component({
    moduleId: module.id,
    selector: 'news-selector-comp',
    templateUrl:'news.html'

})

export class NewsSelectorComponent implements OnInit {

      isLoading = true;
      isError   = false;
      News:any;


      constructor(public newsService:NewsService) { }

}

news.module.ts

news.service.ts

import {Http, Headers} from '@angular/http';
import { Injectable } from '@angular/core';
import { News, NewsImp } from './news';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/map';

@Injectable()
export class NewsService {

_url = '<%= SYSTEM_URL%>/news';
token   = window.localStorage.getItem('token');
user_id = window.localStorage.getItem('user_id');
    constructor(private _http:Http) {

    }

    getNews() : Observable<NewsImp[]> {

        return  this._http.get('https://jsonplaceholder.typicode.com/posts').map(res => res.json());
    }

    postNews() : Observable<News[]> {

      var headers = new Headers();
          headers.append('Content-Type', 'application/json');

      var news = {
        user_id: this.user_id,
        token  : this.token
      };

        return this._http.post(this._url, JSON.stringify(news), {headers:headers}).map( res => res.json().data);
  }

}

推荐答案

我自己也看到过这个问题，但可能是出于不同的原因.我注意到您在这里使用了桶"方法:

I have seen this issue myself, but for perhaps a different reason. I notice you are using the "barrels" approach here:

import { NewsService } from './index';

尝试直接从导出的文件中导入 NewsService 类.这似乎是一个常见问题.

Try importing the NewsService class directly from the file it has been exported from. This seems to be a common issue.

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