GetX - Sample GetNotifier

main.dart

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

void main() {
  runApp(GetMaterialApp(
    initialRoute: '/home',
    getPages: [
      GetPage(
        name: '/home',
        page: () => HomePage(),
      ),
      GetPage(
        name: '/city',
        page: () => CityPage(),
        binding: CityBinding(),
      ),
    ],
  ));
}

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('HOME')),
      body: Center(
        child: RaisedButton(
          onPressed: () => Get.toNamed('/city'),
          child: Text('Go to Cities'),
        ),
      ),
    );
  }
}

class CityBinding extends Bindings {
  @override
  void dependencies() {
    Get.put(Dio());
    Get.put(CityController(dio: Get.find()));
  }
}

class StateModel {
  StateModel({
    this.sigla,
    this.nome,
  });

  String sigla;
  String nome;

  factory StateModel.fromJson(Map<String, dynamic> json) => StateModel(
        sigla: json["sigla"],
        nome: json["nome"],
      );

  Map<String, dynamic> toJson() => {
        "sigla": sigla,
        "nome": nome,
      };

  static List<StateModel> listFromJson(list) =>
      List<StateModel>.from(list.map((x) => StateModel.fromJson(x)));
}

/* class CityController extends GetxController with StateMixin<List<StateModel>> {
  final Dio dio;

  CityController({this.dio});

  @override
  void onInit() {
    super.onInit();
    const String url =
        'https://servicodados.ibge.gov.br/api/v1/localidades/estados';

    dio.get(url).then((result) {
      List<StateModel> data = StateModel.listFromJson(result.data);
      change(data, status: RxStatus.success());
    }, onError: (err) {
      change(null, status: RxStatus.error(err.toString()));
    });
  }
} */

class CityController extends GetNotifier<List<StateModel>> {
  final Dio dio;
  
  // What differentiates GetNotify from StateMix, is the need to start 
  // the Model with a value, that is, the constructor is mandatory
  CityController({this.dio, List<StateModel> initial})
      : super(initial = [StateModel(sigla: 'AA', nome: 'estado1')]);

  getStates() {
    change(null, status: RxStatus.loading());
    const String url =
        'https://servicodados.ibge.gov.br/api/v1/localidades/estados';

    dio.get(url).then((result) {
      List<StateModel> data = StateModel.listFromJson(result.data);
      change(data, status: RxStatus.success());
    }, onError: (err) {
      change(null, status: RxStatus.error(err.toString()));
    });
  }
}

class CityPage extends GetView<CityController> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Cities')),
      body: Container(
        child: controller.obx(
          (state) => Column(
            children: [
              RaisedButton(
                color: Colors.blue,
                onPressed: () => controller.getStates(),
                splashColor: Colors.blueGrey,
                child: Text(
                  'Search Cities',
                  style: TextStyle(
                    color: Colors.white,
                    fontSize: 16,
                  ),
                ),
              ),
              Expanded(
                child: ListView.builder(
                  itemCount: state.length,
                  itemBuilder: (context, index) {
                    return Text(state[index].nome);
                  },
                ),
              ),
            ],
          ),
          onLoading: Center(child: CircularProgressIndicator()),
          onError: (error) => Center(
            child: Text(
              error,
              style: TextStyle(fontSize: 18),
              textAlign: TextAlign.center,
            ),
          ),
        ),
      ),
    );
  }
}