Angular HttpClient 返回期望 observable 而不是 observable

Question

我在使用 HttpClient 时遇到有关返回类型的编译错误。在我的函数中 GetPortfolio , 我期待 GET调用返回 Observable<Portfolio> 类型的 json 对象但它给出了错误:

输入 Observable<HttpEvent<Portfolio>>不可分配给类型 Observable<Portfolio> .输入 HttpEvent<Portfolio>不可分配给类型 Portfolio .输入 HttpProgressEvent不可分配给类型 Portfolio .属性(property)name缺少类型 HttpProgressEvent .

我的代码:

import { Injectable } from '@angular/core';
import { environment } from './environments/environment';
import { HttpClient, HttpHeaders } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';


export interface Portfolio {
  name: string;
  id: string;
}

@Injectable()
export class PortfolioService {

    private httpOptions;

    apiUrl: string;

    constructor(private http: HttpClient) {
      this.apiUrl = environment.apiUrl + "/api/portfolios";

      this.httpOptions = {
        headers: new HttpHeaders(
          {
            'Content-Type': 'application/json',
          })   
      };
    }


    GetPortfolio(portfolioId: string): Observable<Portfolio> {
      return this.http.get<Portfolio>(this.apiUrl + '/${portfolioId}', this.httpOptions);
   }

}

来自 angular hero 教程和文档 HttpClient 请求应该期待 Observable<any> : Angular HttpClient doc

那我是不是做错了什么？或者我应该将返回值设置为 Observable<HttpEvent<Portfolio>> ？

Answer 1

强制转换您的 httpOptions

private httpOptions: {
    headers: HttpHeaders
};

typescript 编译器提取了错误的 get 方法类型 ( src )

/**
* Construct a GET request which interprets the body as JSON and returns the full event stream.
*
* @return an `Observable` of all `HttpEvent`s for the request, with a body type of `T`.
*/
get<T>(url: string, options: {
    headers?: HttpHeaders | {[header: string]: string | string[]},
    observe: 'events',
    params?: HttpParams|{[param: string]: string | string[]},
    reportProgress?: boolean,
    responseType?: 'json',
    withCredentials?: boolean,
}): Observable<HttpEvent<T>>;

当您指定带有标题的类型时，它会提取正确的类型。 ( src )

/**
* Construct a GET request which interprets the body as JSON and returns it.
*
* @return an `Observable` of the body as type `T`.
*/
get<T>(url: string, options?: {
    headers?: HttpHeaders | {[header: string]: string | string[]},
    observe?: 'body',
    params?: HttpParams|{[param: string]: string | string[]},
    reportProgress?: boolean,
    responseType?: 'json',
    withCredentials?: boolean,
}): Observable<T>;