Ionic2 - 设置和检索存储的值失败 [英] Ionic2 - setting and retrieving the value of storage fails

问题描述

我正在设置离子存储的值。但是，我无法检索它。

I am setting the value of storage in ionic. But, I am unable to retrieve it.

这就是我所做的事情

在我的登录服务中

@Injectable()
export class Authservice {
  storage: Storage;

  login(user: UserModel): Observable<any> {
  return this._http.post(this.loginurl + "mobile-login", body)
     .map((response: Response) => {
     let token = response.json().access_token;
     if (token) {
         console.log(token) //this returns a value of the token
       this.storage.set('token', token);

      this.storage.get('token').then((val) => {
        console.log("token value now is"+val);  //this returns nothing
      })
    } else {
      // return false to indicate failed login
      return false;
    }
    })
    //.catch(this.handleError);
 }

另外在我试过的其他服务中

Also in another service I've tried

   this._storage.get('token')
  .then(res=>{
      console.log("in the other area token is"+res)//this is null

    }
  );

我尝试在像这样的构造函数中检索值

I've tried retrieving the value in a constructor like this

authtoken:string;

  constructor(private http: Http, private _storage:Storage) {
this._storage.get('token')
  .then(res=>{
        this.authtoken= res;

    }
  );
  }

然后在组件中我试过了

console.log(this.authtoken)  //still nothing

在我的应用模块中，我还添加了

In my app module I've also added

providers[Storage]

可能是什么问题。我在chrome浏览器上测试。

What could be the problem. I am testing on chrome browser.

推荐答案

这是因为 storage.set 返回一个承诺，这不是一个同步过程。

This because the storage.set returns a promise, it's not a synchronous process.

所以，当你立即调用 storage.get 时，令牌尚未完全保存到存储空间，您什么也得不到。

So, when you call storage.get immediately, the token has not yet been fully saved to storage, and you get nothing.

您可以在存储集成功时创建公共事件。

You can create a public event, when the storage set is successful.

import { BehaviourSubject, Subject } from 'rxjs';

tokenEvent: Subject = new BehaviourSubject(null);

...

this.storage.set('token', token).then(res => this.tokenEvent.next(true));

在其他组成部分：

constructor(private auth: Authservice){}
ngOnInit() {
  this.auth.tokenEvent.subscribe(res => {
    if (res) {
      this.this.storage.get('token')
        .then(token => console.log(token));
    }
  })
}

API文件： https://ionicframework.com/docs/v2/storage/

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