标头未设置在存储承诺中

Question

我正在尝试将标头添加到我的API调用中，但是，我需要获取auth令牌并将其设置为标题。但是，当我尝试运行波纹管代码时，它不会设置它，仅设置内容类型。

import {HttpClient, HttpHeaders} from '@angular/common/http';
import {Component, Injectable} from '@angular/core';
import { Storage } from "@ionic/storage";
import 'rxjs/add/operator/map';
@Injectable()
@Component({
  providers: [HttpClient]
})
export class DataProvider {
  public token:string;
constructor(public http: HttpClient, public storage: Storage) {}
getsomething(){
 let headers = new HttpHeaders();
 headers = headers.set('Content-Type', 'application/json');
 this.storage.get('token').then((val) => {
   this.token = val;
   console.log(this.token);
   headers = headers.set('AuthToken', this.token);
 });
 console.log(headers);
 return this.http.get('http://localhost:54951/getfarms', {
   headers: headers
 });

}

Answer 1

您可以尝试使用observable.flatmap，如下示例

import { HttpClient, HttpHeaders } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { Storage } from "@ionic/storage";
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/mergeMap';
@Injectable()
export class DataProvider {
  constructor(public http: HttpClient, public storage: Storage) { }
  getsomething() {
    return Observable.fromPromise(this.storage.get('token')).flatMap((token) => {
      console.log(token);
      let headers = new HttpHeaders();
      headers = headers.set('Content-Type', 'application/json');
      headers = headers.set('AuthToken', token);
      console.log(headers);
      return this.http.get('http://localhost:54951/getfarms', {
        headers: headers
      });
    });
  }
}

Answer 2

header.set.set（）函数不返回标头实例，因此请执行以下

headers = header.set('AuthToken', this.token); //change the line
headers.set('AuthToken', this.token); //do not reassign the headers object

Answer 3

您无法在调用then后立即使用this.storage.get('token').then中设置的值。承诺不会立即执行处理程序，因为它是异步操作。

getsomething() {
    let headers = new HttpHeaders();
    headers = headers.set('Content-Type', 'application/json');
    return this.storage.get('token').then((val) => {
        this.token = val;
        console.log(this.token);
        headers = headers.set('AuthToken', this.token);

        console.log(headers);
        return this.http.get('http://localhost:54951/getfarms', {
            headers: headers
        });
    });
}

或使用异步/等待

async getsomethingAsync() {
    let headers = new HttpHeaders();
    headers = headers.set('Content-Type', 'application/json');
    let val = await this.storage.get('token')
    this.token = val;
    console.log(this.token);
    headers = headers.set('AuthToken', this.token);

    console.log(headers);
    return this.http.get('http://localhost:54951/getfarms', {
        headers: headers
    });
}