A lightweight state management solution for Flutter that makes handling loading, error, and data states elegant and type-safe using Dart's pattern matching.
Created by p4-k4.
- 🎯 Type-safe state management
- 🔄 Built-in loading state handling
-
⚠️ Elegant error state management - 🎨 Clean and simple API
- 📦 Minimal boilerplate
- 🔍 Pattern matching friendly
- 🎭 Separation of concerns with state files
Add value to your pubspec.yaml:
dependencies:
value: ^0.0.1// Create a Value instance
final counter = Value<int>(0);
// Update the value
counter.setValue(42);
counter.notify();
// Access the value using pattern matching
switch (counter.last) {
case Data(value: final v):
print('Current value: $v');
case Waiting():
print('Loading...');
case Error(error: final e):
print('Error: $e');
case NoData():
print('No data available');
}Here's a complete counter example showing how to use Value with Flutter:
// state.dart
import 'package:value/value.dart';
final counter = Value<int>(0);
void incrementCounter() {
if (counter.lastKnownValue case final value?) {
counter.setValue(value + 1);
counter.notify();
}
}
void decrementCounter() {
if (counter.lastKnownValue case final value?) {
counter.setValue(value - 1);
counter.notify();
}
}
void resetCounter() {
counter.setValue(0);
counter.notify();
}
// main.dart
import 'package:flutter/material.dart';
import 'package:value/value.dart';
import 'state.dart' as app_state;
class CounterWidget extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Subscriber(
(context) => Column(
children: [
Text(
switch (app_state.counter.last) {
Data(value: final v) => '$v',
_ => '0',
},
),
Row(
children: [
FilledButton(
onPressed: app_state.decrementCounter,
child: Text('Decrease'),
),
FilledButton(
onPressed: app_state.resetCounter,
child: Text('Reset'),
),
FilledButton(
onPressed: app_state.incrementCounter,
child: Text('Increase'),
),
],
),
],
),
);
}
}Value makes it easy to handle async operations with built-in loading and error states:
final userProfile = Value<UserProfile>();
Future<void> fetchProfile() async {
userProfile.setWaiting();
userProfile.notify();
try {
final profile = await api.fetchUserProfile();
userProfile.setValue(profile);
} catch (e, s) {
userProfile.setError(e, s);
}
userProfile.notify();
}
// In your widget
Subscriber(
(context) => switch (userProfile.last) {
Data(value: final profile) => ProfileView(profile),
Waiting() => CircularProgressIndicator(),
Error(error: final e) => Text('Error: $e'),
NoData() => Text('No profile data'),
},
)Value provides several state types to handle different scenarios:
-
Data<T>: Contains the actual value -
Waiting<T>: Represents a loading state -
Error<T>: Contains error information -
NoData<T>: Represents absence of data
- Separate State Logic: Keep your Value instances and related functions in separate state files
- Import with Alias: When importing state files, use aliases to make the code more readable
- Pattern Matching: Leverage Dart's pattern matching for clean state handling
-
Notify After Changes: Call
notify()after updating values to trigger UI updates - Use lastKnownValue: For simple value access when you don't need full state information
Contributions are welcome! Please feel free to submit a Pull Request to our GitHub repository.
This project is licensed under the MIT License - see the LICENSE file for details.
Paurini Taketakehikuroa Wiringi
