CODE EXAMPLE FOR DART

initialRoute flutter

runApp(
 MaterialApp(
      initialRoute: 'welcome_screen',
      routes: {
        'welcome_screen': (context) => WelcomeScreen(),
        'login_screen': (context) => LoginScreen(),
        'registration_screen': (context) => RegistrationScreen(),
        'chat_screen': (context) => ChatScreen()
      },
    );
);