typescript - Angular 6 - 如何以正确的方式从另一个异步函数中的异步函数回调中获取价值?
问题描述
我有以下 HTTP 提供程序,它使用 subscribe 方法调用,如下例所示。问题是,在 GET 请求期间,我需要获取保存在本地存储中的令牌值,这是使用 HTTP 提供程序中函数 getToken 中的另一个提供程序发生的。我无法在 HTTP 调用中获取令牌值。我想问一下,请问如何以正确的方式做到这一点?
感谢您的任何建议。
this.httpProvider.doGetRequest(Constants.API_SERVER_URL+Constants.API_ENDPOINT_THREADS)
.subscribe(res => {
console.log(res);
this.loading.dismiss();
}, (error) => {
console.log(error);
this.err = error;
this.loading.dismiss();
this.presentToast();
});
HTTP 提供者类:
@Injectable()
export class HttpProvider {
constructor(public http: HttpClient,
public dataProvider: DataProvider,
public locStor: LocalStorageProvider) {
console.log('Hello HttpProvider Provider');
}
public doGetRequest(url: string) {
return this.http.get(url, this.getHeaders());
}
public doPostRequest(url: string, params: any) {
return this.http.post(url, params);
}
public getHeaders() {
return {
headers: {
'Content-Type': 'application/json',
'Accept': 'application/json',
'Authorization': 'Bearer test',
'token': this.getToken()
},
params: new HttpParams()
};
}
private getToken() {
this.locStor.getValue(Constants.LS_KEY_USER_TOKEN).then((val) => {
return val;
});
//return this.locStor.getValue(Constants.LS_KEY_USER_TOKEN);
//return '222';
//return this.dataProvider.getUser().token;
}
}
更新后的版本
import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import {HttpHeaders} from "@angular/common/http";
import {LocalStorageProvider} from "../local-storage/local-storage";
import {Constants} from "../../app/constants";
import {Headers} from "@angular/http";
import {HttpParams} from "@angular/common/http";
import {DataProvider} from "../data/data";
import 'rxjs/add/observable/fromPromise';
import { Observable } from 'rxjs/Observable';
import {FromObservable} from "rxjs-compat/observable/FromObservable";
import {PromiseObservable} from "rxjs-compat/observable/PromiseObservable";
/*
Generated class for the HttpProvider provider.
See https://angular.io/guide/dependency-injection for more info on providers
and Angular DI.
*/
@Injectable()
export class HttpProvider {
constructor(public http: HttpClient,
public dataProvider: DataProvider,
public locStor: LocalStorageProvider) {
console.log('Hello HttpProvider Provider');
}
public doGetRequest(url: string) {
//return this.http.get(url);
return Observable.fromPromise((this.getHeaders()).flatMap((headers) => {
this.http.get(url, headers);
}));
}
public doPostRequest(url: string, params: any) {
return this.http.post(url, params);
}
public getHeaders() {
/*
return {
headers: {
'Content-Type': 'application/json',
'Accept': 'application/json',
'Authorization': 'Bearer test',
'token': this.getToken
},
params: new HttpParams()
};
*/
return this.locStor.getValue(Constants.LS_KEY_USER_TOKEN).then((val) => {
return {
headers: {
'Content-Type': 'application/json',
'Accept': 'application/json',
'Authorization': 'Bearer test',
'token': val
},
params: new HttpParams()
};
});
}
private getToken() {
this.locStor.getValue(Constants.LS_KEY_USER_TOKEN);
/*
this.locStor.getValue(Constants.LS_KEY_USER_TOKEN).then((val) => {
return val;
});
*/
//return this.locStor.getValue(Constants.LS_KEY_USER_TOKEN);
return '222';
//return this.dataProvider.getUser().token;
}
}
解决方案
我会做这样的事情:
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/fromPromise';
import 'rxjs/add/operator/mergeMap';
@Injectable()
export class HttpProvider {
constructor(public http: HttpClient,
public dataProvider: DataProvider,
public locStor: LocalStorageProvider) {
console.log('Hello HttpProvider Provider');
}
public doGetRequest(url: string) {
return Observable.fromPromise(this.getHeaders()).flatMap((headers) => {
this.http.get(url, headers);
});
}
public doPostRequest(url: string, params: any) {
return this.http.post(url, params);
}
public getHeaders() {
return getToken()
.then((token) => ({
headers: {
'Content-Type': 'application/json',
'Accept': 'application/json',
'Authorization': 'Bearer test',
'token': token,
},
params: new HttpParams()
});
}
private getToken() {
this.locStor.getValue(Constants.LS_KEY_USER_TOKEN)
}
}