typescript - 如何在 Angular 7 中從 API 發送 GET 請求

我正在嘗試使用 Angular 7 中的 HttpClient 來獲取 JSON。代碼運行正常，但我正在嘗試實現註解掉的那幾行，以便直接從 API URL 獲取數據，而不再使用 const IMAGES。

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Injectable()
export class ImageService {

  // public _url: string = "https://jsonplaceholder.typicode.com/photos";
  constructor(
    // public http: HttpClient
  ) {}

  theImages = [];
  // IMAGES = [];
  getImages(){
    // this.IMAGES = this.http.get(this._url);
   return this.theImages = IMAGES.slice(0);
 }
  getImage(id: number){
    // this.IMAGES = this.http.get(this._url);
    return IMAGES.slice(0).find(image => image.id == id);
  }

}
const IMAGES = [
  {
    "albumId": 1,
    "id": 1,
    "title": "accusamus beatae ad facilis cum similique qui sunt",
    "url": "https://via.placeholder.com/600/92c952",
    "thumbnailUrl": "https://via.placeholder.com/150/92c952"
  },
...

錯誤代碼是：

error TS2740: Type 'Observable<Object>' is missing the following properties from type 'any[]': length, pop, push, concat, and 25 more.

答案＃1

你需要從方法中回傳一個 Observable，然後訂閱 ImageService 實例的方法所返回的資料。

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

import { first } from 'rxjs/operators';

@Injectable()
export class ImageService {

  public _url: string = "https://jsonplaceholder.typicode.com/photos";

  constructor(public http: HttpClient) {}

  getImages() {
   return this.http.get(this._url);
 }

  getImage(id: number) {
    return this.http.get(this._url)
                    .pipe(first(item => item.id === id));
  }

}

從你專案中的另一個地方

...
imageService.getImages().subscribe(images => /*...*/)
...