Receive notification indicating that the function is of void type

As a newcomer to angular, I am currently in the process of setting up my authorization module for an ionic project I am developing.

I have made significant progress, but I have encountered an issue with the 'auth' service that I created.

Within my auth.service, I have implemented the following login method:

  login(user){
    this.http.post(this.API_ENDPOINT+'/authenticate', user)
    .map(res => res.json())
    .subscribe(user => {
        this.storeUserCredentials(user); 
        return user;
    })
  }

When attempting to call this method within my login.ts component:

  constructor(public navCtrl: NavController, public navParams: NavParams, private auth: AuthenticationProvider) {
  }

  ionViewDidLoad() {
    console.log('ionViewDidLoad LoginPage');
  }

  userLogin(f){
    this.auth.login(f.value)
      .subscribe(response => {
      this.navCtrl.push('TabsPage');
    })
  }

}

An error is flagged with a red line under '.subscribe' showing the message:

[ts] Property 'subscribe' does not exist on type 'void'.
any

It's worth noting that my ultimate objective is to make a request to the authenticate endpoint, then execute the "storeUserCredentials()", and finally navigate to the tabs page.

Answer №1

A TypeScript error has occurred, indicating a human error was made. The `login` method does not return anything (of type `void`) but is expected to return an observable that includes a `subscribe` method.

In this instance, it is incorrect to call `subscribe` within the `login` method as subscriptions should take place outside of the method.

If `storeUserCredentials` is a synchronous side effect, it can be managed using the `do` operator:


  login(user){
    this.http.post(this.API_ENDPOINT+'/authenticate', user)
    .map(res => res.json())
    .do(user => {
        this.storeUserCredentials(user); 
    })
  }

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