1. create controller with minimal code

controllers/login_controller.dart

                       import 'package:flutter/cupertino.dart';
                        import 'package:get/get.dart';



                        class LoginController extends GetxController {

                          @override
                          void onInit() {
                              super.onInit();

                          }

                          @override
                          void onReady() {}

                          @override
                          void onClose() {}


                        }


                        

2. variables in controller

variable declaration

                        class LoginController extends GetxController {
                            final count = 0;
                            final newCount=0;
                            .... 
                            ....
                        }  
                      

complete code

                      class LoginController extends GetxController {

                         final count = 0;
                         final newCount=0;

                          @override
                          void onInit() {
                              super.onInit();

                          }

                          @override
                          void onReady() {}

                          @override
                          void onClose() {}


                          }

                          

1. Update(): Using this, widgets can listen to the changes made by the methods defined in controller. It is similar to notifyListeners in providers
2. onInit(): It is called immediately after the widget is allocated memory.
3. onReady(): It is called immediately after the widget is rendered on screen.
4. onClose(): It is called just before the controller is deleted from memory.

observable variables

                          final name = ''.obs;

                          final isLogged = false.obs;

                          final count = 0.obs;

                          final balance = 0.0.obs;

                          final number = 0.obs;

                        

3. access variable in view

1. import login_controller.dart in view page screens/login.dart

                         import 'package:getx_restaurant/controllers/login_controller.dart';
                        

2. add dependency injection for access the controller

                        LoginController logincontroller = Get.put(LoginController());
                        

3. access the variable in controller

                        logincontroller.name
                        

complete code

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

import 'package:getx_restaurant/controllers/login_controller.dart';  //1.  added new line



class LoginScreen extends StatelessWidget {
  LoginScreen({Key? key}) : super(key: key); 
  LoginController logincontroller = Get.put(LoginController());  //2.  added new line

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Flutter Demo',
      home: Scaffold(
        backgroundColor: Colors.yellow,
        appBar: AppBar(title: const Text("My App Title")),
        body: SafeArea(
            child: Column(
                children: [

                  Container(
                    padding: EdgeInsets.all(15),
                    child: TextField(
                        obscureText: true,
                        decoration: InputDecoration(
                          border: OutlineInputBorder(),
                          labelText: 'Username',
                          hintText: 'Enter Username',
                        ),
                      ),
                  ),

                  Padding(
                    padding: EdgeInsets.all(15),
                    child: TextField(
                      obscureText: true,
                      decoration: InputDecoration(
                        border: OutlineInputBorder(),
                        labelText: 'Password',
                        hintText: 'Enter Password',
                      ),
                    ),
                  ),


                  ElevatedButton(
                    onPressed: () {
                      Get.to(()=>RegisterScreen());
                    },
                    child: Text(logincontroller.name),  //3.  added new line
                  ),

                  Row(

                      children: [
                        SizedBox(width: 50),
                        Expanded(
                          child:ElevatedButton(
                            onPressed: () {

                            },
                            child: Text('New Account'),
                          ),
                        ),
                        SizedBox(width: 50),
                        Expanded(
                          child:ElevatedButton(
                            onPressed: () {

                            },
                            child: Text('New Account'),
                          ),
                        ),
                        SizedBox(width: 50),


                      ]

                  )

                ]
            )
        ),
      ),
    );
  }



}

4. methods in controller

function definition

  ... 
  List<String> todoItems = []; 
    ..... 

  void addTodo() {
        int index = todoItems.length;
        todoItems.add('Item' + index.toString());
        /** Notify changes in method, variables to the views **/
        update(); 
  }

function call from view

onPressed: () {
    logincontroller.addTodo();
},
              

5. Observable variable

Observable Variable declaration in controller

              final followerCount = 0.obs;

access Observable variable from view

      body: Container(
        child: Obx(() => Center(child: Text(logincontroller.count.toString()))),
      ),

We can use inside the container(), row(), column(), padding() etc

6. Inputbox variable

variable declaration

final storeNameEditingController = TextEditingController();
  final reviewEditingController = TextEditingController();
  final followerController = TextEditingController();
  final reviewNameController = TextEditingController();
    

access from view

                  Container(
                    padding: EdgeInsets.all(15),
                    child: TextField(
                        obscureText: true,
                        decoration: InputDecoration(
                            border: OutlineInputBorder(),
                            labelText: 'Username',
                            hintText: 'Enter Username',
                            controller: logincontroller.storeNameEditingController,
                        ),
                      ),
                  ),