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effects.dart
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effects.dart
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import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:result_notifier/result_notifier.dart';
/// Simple example demonstrating the use of [EffectNotifier]s, such as [CombineLatestNotifier] and
/// [AsyncEffectNotifier], to build more complex chains of processing.
void main() => runApp(const ChainsAndEffectsExampleApp());
class ChainsAndEffectsExampleApp extends StatelessWidget {
const ChainsAndEffectsExampleApp({super.key});
@override
Widget build(BuildContext context) {
return const MaterialApp(
title: 'SimpleResultNotifierExampleApp',
home: ActivityPage(),
);
}
}
/// Displays a random activity
class ActivityPage extends StatefulWidget {
const ActivityPage({super.key});
@override
State<StatefulWidget> createState() => ActivityState();
}
class ActivityState extends State<ActivityPage> {
final ResultNotifier<String> name1 = ResultNotifier(data: '');
final ResultNotifier<String> name2 = ResultNotifier(data: '');
late final ResultNotifier<String> result;
String? currentName;
@override
void initState() {
ResultNotifier<String> activity = name1.asyncEffect(_fetchActivityEffect);
result = activity.combineLatest(name2,
combineData: (sources) => '${sources[0]} with ${sources[1]}');
super.initState();
}
Future<String> _fetchActivityEffect(
ResultNotifier<String> notifier, String input) async {
// ignore: avoid_print
currentName = input;
await Future.delayed(const Duration(milliseconds: 500)); // Dramatic Pause
if (currentName != input) {
print('Name changed - aborting activity fetch');
}
print('Fetching for random activity for "$input"');
final response =
await http.get(Uri.parse('https://www.boredapi.com/api/activity/'));
final json = jsonDecode(response.body) as Map<String, dynamic>;
return '$input wants to ${json['activity'] as String}';
}
@override
Widget build(BuildContext context) {
final size = MediaQuery.sizeOf(context);
return Scaffold(
appBar: AppBar(
title: const Text('Activity suggestion'),
),
body: Center(
child: SizedBox(
width: size.width > 500 ? 500 : size.width,
child: Column(
children: [
TextField(
decoration: const InputDecoration(hintText: 'Name 1'),
onChanged: (value) => name1.data = value,
),
TextField(
decoration: const InputDecoration(hintText: 'Name 2'),
onChanged: (value) => name2.data = value,
),
const SizedBox(height: 20),
Text('Result: ',
style: Theme.of(context).textTheme.headlineMedium),
result.builder((context, result, child) => switch (result) {
Data(data: var d) =>
Text(d, style: Theme.of(context).textTheme.bodyLarge),
Error(error: var e) => Text('Error: $e'),
Loading() => const CircularProgressIndicator(),
}),
],
),
),
),
);
}
}