How can I implement a GoRouter example with login and register functionality?

Implementing a GoRouter example with login and register functionality involves setting up routes, handling authentication state, and creating UI components for login and registration. Here's a breakdown of how you can achieve this:

1. Set up GoRouter:

- First, you need to define your routes using GoRouter. This includes routes for the login page, registration page, and the main application page. You'll also need a way to check if a user is authenticated before allowing access to certain routes.

2. Authentication State Management:

- You'll need a mechanism to manage the user's authentication state. This could be a simple boolean flag or a more complex state management solution like Provider or Riverpod. The GoRouter's `redirect` function will use this state to determine which route to navigate to.

3. Login and Register Pages:

- Create separate UI components for the login and registration pages. These pages will contain forms for user input and logic to handle authentication requests.

4. Example Code Snippets:

// Example using a simple boolean for authentication state
bool _isAuthenticated = false;

// Define routes
final _router = GoRouter(
  redirect: (context, state) {
    if (!_isAuthenticated) {
      if (state.location != '/login' && state.location != '/register') {
        return '/login';
      }
    }
    return null;
  },
  routes: [
    GoRoute(
      path: '/',
      builder: (context, state) => HomePage(),
    ),
    GoRoute(
      path: '/login',
      builder: (context, state) => LoginPage(),
    ),
    GoRoute(
      path: '/register',
      builder: (context, state) => RegisterPage(),
    ),
  ],
);

// Example Login Function
void login(String username, String password) {
  // Perform authentication logic here
  if (username == 'test' && password == 'password') {
    _isAuthenticated = true;
    _router.go('/'); // Navigate to home page after successful login
  }
}

5. Navigation:

- Use `context.go('/route')` or `context.push('/route')` to navigate between pages. After successful login or registration, navigate the user to the main application page.

6. Logout:

- Implement a logout function that sets the authentication state to false and navigates the user back to the login page.

7. Error Handling:

- Handle errors gracefully, such as invalid login credentials or registration failures, and provide feedback to the user.

By following these steps, you can create a robust authentication flow using GoRouter. Remember to adapt the code snippets to your specific needs and consider using a more advanced state management solution for larger applications.

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