🎯 Dart에서 Stream과 Future 활용하여 실시간 데이터 처리하기

// 1단계: Stream 기본 사용
import 'dart:async';
void main() {
  final stream = Stream.fromIterable(["A", "B", "C"]);
  stream.listen((data) => print('받은 데이터: $data'));
}

// 2단계: FutureBuilder 활용
import 'package:flutter/material.dart';
import 'dart:async';

class FutureBuilderExample extends StatelessWidget {
  final Future<String> _future = Future.delayed(Duration(seconds: 2), () => "완료");

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('FutureBuilder 예제')),
      body: Center(
        child: FutureBuilder<String>(
          future: _future,
          builder: (context, snapshot) {
            if (snapshot.hasData) return Text(snapshot.data!);
            return CircularProgressIndicator();
          },
        ),
      ),
    );
  }
}

// 3단계: Stream + Future 결합
import 'dart:async';
Stream<String> dataStream() {
  final controller = StreamController<String>();
  Timer(Duration(seconds: 3), () => controller.add("데이터 전송됨"));
  return controller.stream;
}

Future<void> processData() async {
  try {
    final result = await dataStream().first;
    print('처리 결과: $result');
  } catch (e) {
    print('에러 발생: $e');
  }
}

// 4단계: 실시간 UI 통합
import 'package:flutter/material.dart';
class RealtimeDataScreen extends StatefulWidget {
  @override
  _RealtimeDataScreenState createState() => _RealtimeDataScreenState();
}

class _RealtimeDataScreenState extends State<RealtimeDataScreen> {
  final StreamController<String> _controller = StreamController();
  String _latestData = '기본 데이터';

  @override
  void initState() {
    super.initState();
    Timer.periodic(Duration(seconds: 2), (_) => _controller.add(DateTime.now().toString()));
    _controller.stream.listen((data) {
      setState(() => _latestData = data);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('실시간 데이터')), 
      body: Center(child: Text(_latestData)),
    );
  }
}