Wordpress Angular 5 HTTP加载json文件错误

新闻服务.ts

import { Injectable } from '@angular/core';
    import { HttpClient } from '@angular/common/http';
    import { INews } from './inews';
    import { Observable } from 'rxjs';
    import { map } from 'rxjs/operators';

    @Injectable({
      providedIn: 'root'
    })
    export class NewsserviceService {
      public _url = 'http://localhost/admin/demo/api/get_posts/';
      constructor( public http: HttpClient) { }
      getNews(): Observable<INews[]> {
        return this.http.get<INews[]>(this._url).pipe(map(res => res.json()));
      }
     }

import { Component, OnInit } from '@angular/core';
import { NewsserviceService } from './newsservice.service';

@Component({
  selector: 'app-news-ticker',
  templateUrl: './news-ticker.component.html',
  styleUrls: ['./news-ticker.component.scss']
})
export class NewsTickerComponent implements OnInit {
  public news: any[];
  constructor(private newsservice: NewsserviceService) { }

  ngOnInit() {
    this.loadNews();
  }
  loadNews(): void {
    this.newsservice.getNews().subscribe(res => this.news = res);

  }

}

newscomponent.html

<section class="news-ticker">
  <div class="container">
    <div class="row">
      <div class="col-md-12">
        <div class="ticker">
          <strong class="pull-left">news flash</strong>
          <ul>
            <li *ngFor='let news of news'>
              {{news.content}}
            </li>
          </ul>
        </div>
      </div>
    </div>
  </div>
</section>

新闻快讯


{{news.content}

控制台错误

错误类型错误：res.json不是函数 在MapSubscriber.project（newservice.service.ts:14） 在MapSubscriber.push../node_modules/rxjs/_esm5/internal/operators/map.js.MapSubscriber.\u next（map.js:75） 在MapSubscriber.push../node_modules/rxjs/_esm5/internal/Subscriber.js.Subscriber.next（Subscriber.js:93） 在MapSubscriber.push../node_modules/rxjs/_esm5/internal/operators/map.js.MapSubscriber._next（map.js:81） 在MapSubscriber.push../node_modules/rxjs/_esm5/internal/Subscriber.js.Subscriber.next（Subscriber.js:93） 在FilterSubscriber.push../node_modules/rxjs/_esm5/internal/operators/filter.js.FilterSubscriber.\u下一步（filter.js:85） 在FilterSubscriber.push../node_modules/rxjs/_esm5/internal/Subscriber.js.Subscriber.next（Subscriber.js:93） 在MergeMapSubscriber.push../node_modules/rxjs/_esm5/internal/operators/mergeMap.js.MergeMapSubscriber.notifyNext（mergeMap.js:136） 在InnerSubscriber.push../node_modules/rxjs/_esm5/internal/InnerSubscriber.js.InnerSubscriber.\u下一步（InnerSubscriber.js:20）

---

在InnerSubscriber.push../node_modules/rxjs/_esm5/internal/Subscriber.js.Subscriber.next（Subscriber.js:93）

您最好写一些关于您的问题的信息，但您的问题是指

 getNews(): Observable<INews[]> {
            return this.http.get<INews[]>(this._url).pipe(map(res => res.json()));
      }

由于该方法提供了可观察性，我们应该在目标组件中订阅它，您只需执行以下操作：

loadNews() {
    this.newsservice.getNews().subscribe(res => this.news = res);

  }

---

当我改为使用上述代码处理本地json文件时，当我使用来自服务器的json api时，显示加载失败：请求的资源上不存在“Access Control Allow Origin”头。因此，不允许访问源“”。

loadNews() {
    this.newsservice.getNews().subscribe(res => this.news = res);

  }