I wonder about the origin of the Unsubscribe type

Hello, I am in the process of determining the user's availability status within the component. My goal is to return true if the user is logged in, otherwise return false.

I am utilizing Firebase's method to monitor the user's login state:

firebase.auth().onAuthStateChanged

Below is the snippet of code I have written for this task:

const isLoggedIn = firebase.auth().onAuthStateChanged(user => {
    console.log(!!user)
    return !!user;
  });

  const showSaveTheProgressButton:boolean = isLoggedIn;

However, when attempting to return a boolean value from this function, something unexpected is being returned instead of a boolean:

Type 'false | Unsubscribe' is not assignable to type 'boolean'.

The program is throwing an error message indicating that it is receiving something other than a boolean, specifically 'Unsubscribe.'

This leads me to believe that the program should not be returning 'Unsubscribe,' right?

typescriptfirebasefirebase-authentication

Answer №1

You're not utilizing the onAuthStateChanged method correctly. It doesn't directly return the value inside its callback. Instead, it immediately returns an unsubscribe function, regardless of the callback's logic. The purpose is to trigger actions based on changes in the user's authentication state.

If you need the current user object right away (when a user is signed in), you can use firebase.auth().currentUser. Keep in mind that this will initially be null when the page loads. To track when the user object becomes available, you should utilize onAuthStateChanged.

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