我编写了一个 http 服务。

它包含一个函数 请求调用 ：

import { Injectable } from '@angular/core';
import { HttpClient, HttpErrorResponse } from '@angular/common/http';
import { ApiMethod, AuthEndPoints } from '../conts';
import { environment } from '../../../../environments/environment';
import { catchError } from 'rxjs/operators';

@Injectable({
  providedIn: 'root'
})
export class HttpService {

  constructor(private http: HttpClient) {
  }

  requestCall(method: ApiMethod, api: AuthEndPoints, data?: any): any {
    let response;
    switch (method) {
      case ApiMethod.GET:
        response = this.http.get(`${environment.baseUrl}${api}`).pipe(
          catchError(err => this.handleError(err, this))
        );
        break;
      case ApiMethod.POST:
        response = this.http.post(`${environment.baseUrl}${api}`, data).pipe(
          catchError(err => this.handleError(err, this))
        );
        break;
      case ApiMethod.PUT:
        response = this.http.put(`${environment.baseUrl}${api}`, data).pipe(
          catchError(err => this.handleError(err, this))
        );
        break;
      case ApiMethod.DELETE:
        response = this.http.delete(`${environment.baseUrl}${api}`).pipe(
          catchError(err => this.handleError(err, this))
        );
        break;
    }
  }

在我的登录组件中，我按如下方式调用此方法：

import { Injectable } from '@angular/core';
import { Router } from '@angular/router';
import { HttpService } from '../../core/services/http/http.service';
import { ApiMethod, AuthEndPoints } from '../../core/services/conts';
import { StorageService } from '../../core/services/storage/storage.service';


@Injectable({
  providedIn: 'root'
})
export class AuthService {

  constructor(
    private http: HttpService,
    private router: Router,
    private storage: StorageService
  ) { }

  login(loginForm: LoginForm): any {
    this.http.requestCall(ApiMethod.POST, AuthEndPoints.LOGIN, loginForm).subscribe(res => {
      this.storage.saveToken(res.auth_token);
      this.router.navigate(['/dashboard']);
    }, (error) => {console.log(error)})
  }

当我登录时，我收到以下错误消息：

core.js:6456 ERROR TypeError: Cannot read property 'subscribe' of undefined

at AuthService.login (auth.service.ts:35)

at LoginComponent.onSubmit (login.component.ts:50)...

我不太明白是什么触发了这个错误。

我尝试了另一种没有 requestCall() 方法的方法，这个方法也有效。但我想用这种方法。

你怎么看？