如何使用httpClient在Angular7中封装请求管理器？

npm install @angular/common@7.0.0

ng generate service http-manager

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

constructor(private http: HttpClient) { }

get(url: string, params?: any): Observable<any> {
  let httpOptions = {
    headers: new HttpHeaders({
      'Content-Type': 'application/json'
    }),
    params: new HttpParams()
  };

  if (params) {
    for (let key in params) {
      httpOptions.params = httpOptions.params.set(key, params[key]);
    }
  }

  return this.http.get(url, httpOptions);
}

import { HttpManagerService } from './http-manager.service';

constructor(private httpManager: HttpManagerService) { }

ngOnInit() {
  this.httpManager.get('https://api.example.com/data').subscribe(response => {
    console.log(response);
  });
}