generics sample

generics.dart

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});
  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> with ChangeNotifier {
  int _index = 0;
  String _value = '_value';
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
          child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          TextButton(
            onPressed: () {
              genericsSample('int');
            },
            child: Text('$_index'),
          ),
          TextButton(
            onPressed: () {
              genericsSample('string');
            },
            child: Text(_value),
          ),
        ],
      )),
    );
  }

  // this is generics
  T genericsSample<T>(String value) {
    switch (value) {
      case 'int':
        _index += 1;
        _notify();
        return _index as T;
      case 'string':
        _value = _index.toString();
        _notify();
        return _value as T;
    }
    return 0 as T;
  }

  _notify() {
    setState(
      () => notifyListeners(),
    );
  }
}

2023-05-11.7.16.02.mov