离子存储以 Aync 方式获取值 [英] ionic storage getting values in Aync way

问题描述

我正在尝试在离子存储中获取 2 个值存储，但该值以异步方式检索，并且在检索值之前发生请求

I am trying to get 2 values stores in ionic storage , but the value are retrived in async way and request is happening before the values are retrived

这里是Auth，url在离子存储中

Here Auth, url are in ionic storage

import { Injectable } from '@angular/core';
import { Http, Response } from '@angular/http';
import 'rxjs/add/operator/map';
import {Headers} from '@angular/http';
import { Storage } from '@ionic/storage';

/*
  Generated class for the SeasonService provider.

  See https://angular.io/docs/ts/latest/guide/dependency-injection.html
  for more info on providers and Angular 2 DI.
*/
@Injectable()
export class SeasonService {
Auth;
url;

  constructor(public http: Http, public storage: Storage) {
    console.log('Inside SeasonService constructor');

    this.storage.get('Auth').then((Auth) => {
      console.log('Retrived Auth is', Auth);
      this.Auth = Auth;

    } );
    this.storage.get('url').then((url) => {
      console.log('Retrived url is', url);
      this.url = url;
    } );
   }

  public getSeasonList() {

          console.log('Season Auth is', this.Auth);
          console.log('Season url is', this.url);
        const headers: Headers = new Headers();
        headers.append('Authorization', 'Basic ' + this.Auth);
        headers.append('Content-Type', 'application/json');
        return (this.http.get('http://' + this.url +'/Windchill/servlet/rest/rfa/instances?module=SEASON',
        {headers: headers}).
        map((response: Response) =>  response.json()));
      }
}

输出是这样的

Here
auth-service.ts:49 Headers {_headers: Map(2), _normalizedNames: Map(2)}
auth-service.ts:77 There
season-service.ts:19 Inside SeasonService constructor
season-service.ts:34 Season Auth is undefined
season-service.ts:35 Season url is undefined
season-service.ts:22 Retrived Auth is d2NhZG1pbjp3Y2FkbWlu
season-service.ts:27 Retrived url is 192.168.146.52
auth-service.ts:79 Your CSRF is laxYnd5XE6d/r+W655087+8dY5Irxc7do94fxLgvY5ImgNeIwsgI1bYaQdAzxZDM5sMZsqgbXppFntGDoJhrq+puJJROnN+N1MEcy7d4Js8ozs7Oxpwfpe0zRvcIktg=
auth-service.ts:82 Your Auth is d2NhZG1pbjp3Y2FkbWlu
auth-service.ts:85 Your url is 192.168.146.52

推荐答案

在发出请求之前，您必须等待两个promise 都得到解决.首先将您的存储代码移动到某个 init 方法.

You have to wait for both promise to get resolved before make request. First move your storage code to some init method.

public init(){

let promiseList: Promise<any>[] = [];
promiseList.push(
 this.storage.get('Auth').then((Auth) => {
      console.log('Retrived Auth is', Auth);
      this.Auth = Auth;

    } ));
promiseList.push(
    this.storage.get('url').then((url) => {
      console.log('Retrived url is', url);
      this.url = url;
    } ));

return Promise.all(promiseList);
}

现在在 getSesonList 之前调用 init 方法如下:

Now call init method before getSesonList as followed:

this.sessionService.init().then((values)=>{
this.sessionService.getSeasonList();
});

这将确保在解决两个存储承诺后调用 getSeasonList 方法.

this will make sure that the getSeasonList method will be called after both storage promises get resolved.

显然你应该放一些错误处理代码，但它在你身上.

Obviously you should put some error handling code but its upon you.

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