如何在Angular 5中将标头设置为HttpHeaders

问题描述

我试图弄清楚如何处理HttpHeaders上的标头，以通过HttpClient将其用于HTTP请求.

I'm trying to figure out how to handle headers on HttpHeaders to use them for http requests via HttpClient.

const headers = new HttpHeaders();
headers.append('foo', 'bar');
headers.set('foo', 'bar');

console.log(headers.get('foo')) // null

它只能通过这种方式工作:

it works only this way:

const headers = new HttpHeaders().set('foo', 'bar');
console.log(headers.get('foo')) // bar

是否有添加标题的特殊方法?还是一个错误?

Is there a special way to add headers? Or it is a bug?

推荐答案

这对我有用:

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

const url = `https://sampleapi.com`;

@Injectable()
export class BasicService {
  private _headers = new HttpHeaders().set('Content-Type', 'application/json');
  constructor(private httpClient: HttpClient) { }

  getWithHeader(): Observable<any> {
    const headers = this._headers.append('foo', 'Bar');
    return this.httpClient.get<any>(url, { headers : headers });
  }
}

这从一个私有变量开始，该私有变量使用set保留了头的初始集合.然后使用append在进行Http调用之前添加其他标头.

This starts with a private variable that holds the initial set of headers, using set. Then uses append to add an additional headers before making the Http call.

请注意，append返回一个HttpHeaders对象，这就是为什么我将输出分配给const的原因.仅运行append并认为现有的_headers将被更改，不会给您预期的结果.我确实确认HttpHeaders是不可变的.

Note that append returns an HttpHeaders object, which is why I assign the output to a const. Just running append by itself, thinking that the existing _headers will be changed, will not give you the results you might expect. I did confirm that HttpHeaders are immutable.

从 HttpHeaders 文档:不可变的Http标头集，延迟解析.

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