function-pointers-in-flutter.dart

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import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';

typedef LoginOrRegisterFunction = Future<UserCredential> Function({
  required String email,
  required String password,
});

Future<bool> _registerOrLogin({
  required LoginOrRegisterFunction fn,
  required String email,
  required String password,
}) async {
  try {
    await fn(
      email: email,
      password: password,
    );
    // do some processing
    return true;
  } catch (e) {
    // handle the error here
    return false;
  } finally {
    // perform cleanup
  }
}

Future<bool> register({
  required String email,
  required String password,
}) =>
    _registerOrLogin(
      fn: FirebaseAuth.instance.createUserWithEmailAndPassword,
      email: email,
      password: password,
    );

Future<bool> login({
  required String email,
  required String password,
}) =>
    _registerOrLogin(
      fn: FirebaseAuth.instance.signInWithEmailAndPassword,
      email: email,
      password: password,
    );