declare 1.0.1

A lightweight, SwiftUI-inspired Prop management library for Flutter. Powered by Prop, ViewModel, and Published.

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📦 Declare

SwiftUI-inspired reactive state management for Flutter — powered by State<T>, Published<T>, Computed<T>, and ViewModel concepts.

Simple. Lightweight. Declarative. No external dependencies.

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✨ Features

✅ Minimal, expressive syntax inspired by SwiftUI ✅ Prop<T> – reactive local state with automatic notification ✅ Published<T> – nullable reactive state that notifies parent ViewModel ✅ Computed<T> – derived reactive values based on dependencies ✅ ViewModel – lifecycle-aware logic container managing reactive states ✅ DeclareView<T> – widget that creates and listens to a ViewModel, rebuilding on changes ✅ Observer<T> – widget that listens to any ValueListenable<T> and rebuilds on changes ✅ Pure Dart and Flutter — no third-party dependencies ✅ Designed for clean MVVM architecture

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🧱 Getting Started

Add declare to your pubspec.yaml:

dependencies:
  declare: ^1.0.0

Using DeclareView with a ViewModel

class CounterViewModel extends ViewModel {
  late final Prop<int> count;

  CounterViewModel() {
    count = Prop<int>(0);
  }

  void increment() => count.update(count.value + 1);

  @override
  void onInit() {
    print('CounterViewModel initialized');
  }

  @override
  void onDispose() {
    print('CounterViewModel disposed');
  }
}

DeclareView<CounterViewModel>(
  create: () => CounterViewModel(),
  builder: (context, vm) {
    return Column(
      children: [
        Observer<int>(
          observable: vm.count,
          builder: (context, value) => Text('Count: $value'),
        ),
        ElevatedButton(
          onPressed: vm.increment,
          child: Text('Increment'),
        ),
      ],
    );
  },
);

Reacting to any ValueListenable<T> with Observer

Observer<int>(
  observable: someValueListenable,
  builder: (context, value) => Text('Value: $value'),
);

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📚 API Overview

• Prop<T> – a reactive wrapper around a value with update and transform methods. Notifies listeners on changes.
• Published<T> – nullable reactive state, notifies its parent ViewModel when changed.
• Computed<T> – a derived reactive value computed from one or more dependencies (ValueListenables).
• ViewModel – base class managing multiple reactive states and computed values, with lifecycle hooks onInit() and onDispose().
• DeclareView<T extends ViewModel> – Flutter widget that instantiates a ViewModel, calls its lifecycle, and rebuilds on change.
• Observer<T> – widget that listens to any ValueListenable<T> and rebuilds when the value changes.

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⚙️ Lifecycle

• ViewModel.onInit() is called once when DeclareView initializes.
• ViewModel.onDispose() is called when DeclareView disposes.
• Reactive states notify their parent ViewModel, which triggers widget rebuilds.

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🛠️ Advantages

• Familiar MVVM pattern with reactive data binding
• No extra dependencies, pure Flutter code
• Clear separation of UI and business logic
• Easy to test ViewModels without Flutter widgets

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