androidflutterfirebase

Type mismatch error mapping Firebase authStateChanges to UserModel in Flutter


enter image description hereI'm currently working on a Flutter app that utilizes Firebase for authentication. I have a custom UserModel class to represent user data within my application. However, I'm encountering a type mismatch error when trying to map the authStateChanges stream from Firebase to my UserModel class.

The relevant code snippet is as follows:

Stream\<UserModel?\> get user { return \_auth.authStateChanges().map\<UserModel?\>(\_getUserFromFirebase); }

In the code above, I'm attempting to map the authStateChanges stream to a UserModel object using the \_getUserFromFirebase method. This method takes a UserModel parameter and returns a UserModel? object based on the provided User? object.

However, I'm getting the following error message:

The argument type 'UserModel? Function(UserModel?)' can't be assigned to the parameter type 'UserModel? Function(User?)'

I believe the error is related to a type mismatch between the expected function type and the actual function being used in the map method.

I have a fromFirebaseUser factory method in my UserModel class, which constructs a UserModel object from a User? object received from Firebase. Here's the relevant code snippet from my UserModel class:

UserModel? _getUserFromFirebase(UserModel? user) { return user != null ? UserModel(uid: user.uid) : null; }

I'm seeking guidance on how to resolve this type mismatch error and successfully map the authStateChanges stream to my UserModel class.

Any assistance or suggestions would be greatly appreciated. Thank you!

In my code, I made the following attempt to map the authStateChanges() stream to a UserModel object:

Stream<UserModel?> get user { return _auth.authStateChanges().map(_getUserFromFirebase); }

I expected this code to compile successfully and provide a Stream<UserModel?> where each emitted value is an instance of the UserModel class. The _getUserFromFirebase function is responsible for converting a User? object to a UserModel? object.

However, when running the code, a type mismatch error occurs:

The argument type 'UserModel? Function(UserModel?)' can't be assigned to the parameter type 'UserModel? Function(User?)'

This error message suggests that there is a mismatch between the expected function type and the actual function provided. The function signature required by the map method is 'UserModel? Function(User?)', but the function _getUserFromFirebase has a signature of 'UserModel? Function(UserModel?)'.

I attempted to modify the _getUserFromFirebase function and explicitly specify the type argument for the map method. However, these attempts did not resolve the type mismatch error.enter image description here


Solution

  • You're encountering a type mismatch error because the map method expects a function that takes a User? parameter and returns a UserModel?, but your _getUserFromFirebase function takes a UserModel? parameter. To resolve this issue, you can adjust your code to correctly map the User? objects from the authStateChanges stream to your UserModel objects.

    Stream<UserModel?> get user { return _auth.authStateChanges().map<UserModel?>((user) { return _getUserFromFirebase(user); }); }

    In this code, we explicitly specify the function type for the map method by providing a lambda function that takes a User? as an argument and calls your _getUserFromFirebase function with it. This should resolve the type mismatch error and give you a Stream<UserModel?> where each emitted value is an instance of the UserModel class.

    Make sure to replace the code in your project with the modified code snippet above, and it should work as expected.

    This should help you resolve the issue and map the authStateChanges stream to your UserModel class successfully. If you have any more questions or need further assistance, feel free to ask.