depend

depend is a library for dependency management in Flutter applications. It provides a convenient way to initialize and access services and repositories via InheritedWidget.

---

Features 🚀

• Dependency Initialization: Prepare all dependencies before the app launches.
• Global Access: Access dependencies from anywhere in the widget tree.
• Parent Dependencies Support: Easily create nested or connected dependencies.
• Ease of Use: Integrate the library into existing code with minimal changes.

---

Table of Contents

• Features 🚀
• Table of Contents
• Installation
• Usage Examples
  • Example 1: Simple Initialization
    • Step 1: Define the Dependency
    • Step 2: Define the DependencyFactory
    • Step 3: Use DependencyScope
    • Step 4: Access the Dependency in a Widget
  • Example 2: DependencyProvider
  • Example 3: DependencyScope
  • Example 4: Lazy Initialization
    • Using LazyGet for Synchronous Dependencies
    • Using LazyFutureGet for Asynchronous Dependencies
• Migration Guide
• Code Coverage

---

Installation

Add the library to the pubspec.yaml of your project:

dependencies:
  depend: ^latest_version

Install the dependencies:

flutter pub get

---

Usage Examples

Example 1: Simple Initialization

Step 1: Define the Dependency

Create a class that extends DependencyContainer and initialize your dependencies:

class RootContainer extends DependencyContainer {
  final ApiService apiService;

  RootContainer({required this.apiService});


  void dispose() {
    apiService.dispose();
  }
}

Step 2: Define the DependencyFactory

Create a class that extends DependencyContainer and initialize your dependencies:

class RootDependencyFactory extends DependencyFactory<RootContainer> {
  
  Future<RootContainer> create() async {
    return RootContainer(
      apiService: await ApiService.initialize(),
    );
  }
  
  // or

  RootContainer create() {
     return RootContainer(
        apiService: ApiService.initialize(),
     );
  }
}

Step 3: Use DependencyScope

Wrap your app in a DependencyScope to provide dependencies:

void main() {
  runApp(
    DependencyScope<RootContainer, RootFactory>(
       factory: RootFactory(), 
       placeholder: const Center(child: CircularProgressIndicator()), 
       builder: (BuildContext context) => const MyApp(),
    ),
  );
}

Step 4: Access the Dependency in a Widget

You can now access the dependency using DependencyProvider anywhere in the widget tree:

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final apiService = DependencyProvider.of<RootContainer>(context).apiService;

    return FutureBuilder(
      future: apiService.getData(),
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const CircularProgressIndicator();
        } else if (snapshot.hasError) {
          return Text('Error: ${snapshot.error}');
        }

        return Text('Data: ${snapshot.data}');
      },
    );
  }
}

---

Example 2: DependencyProvider

final RootContainer dep = await RootFactory().create();

DependencyProvider<RootContainer>(
  dependency: dep,
  builder: () => YourWidget();
  // or
  child: YourWidget()
)

class YourWidget extends StatelessWidget {
  @override
  Widget build(BuildContext) {
    root = DependencyProvider.of<RootContainer>(context);
    ...
  }
}

Example 3: DependencyScope

DependencyScope<RootContainer, RootFactory>(
      factory: RootFactory(),
      builder: (BuildContext context) => Text('Inject'),
      placeholder: Text('Placeholder'),
      errorBuilder: (Object? error) => Text('Error'),
    ),

---

Example 4: Lazy Initialization

The library provides LazyGet and LazyFutureGet classes for lazy initialization of services. Dependencies are created only when they are first accessed, which improves application startup time.

Using LazyGet for Synchronous Dependencies

class RootContainer extends DependencyContainer {
  // Service will be created only when accessed for the first time
  final LazyGet<ApiService> apiService;
  final LazyGet<DatabaseService> database;
}

class RootDependencyFactory extends DependencyFactory<RootContainer> {
  RootContainer create() {
     return RootContainer(
        apiService: lazyGet(ApiService.initialize),
        database: lazyGet(DatabaseService.initialize),
     );
  }
}

// Usage in widgets
class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final container = DependencyProvider.of<RootContainer>(context);
    
    // ApiService is created only at this moment
    final api = container.apiService();
    
    return Text('Service initialized: ${api}'); // Instance: ApiService
  }
}

Using LazyFutureGet for Asynchronous Dependencies

class RootContainer extends DependencyContainer {
  final LazyFutureGet<DatabaseService> database;
      
  final LazyFutureGet<AuthService> authService;
}

class RootDependencyFactory extends DependencyFactory<RootContainer> {
  RootContainer create() {
     return RootContainer(
        apiService: lazyFutureGet(ApiService.initialize),
        database: lazyFutureGet(DatabaseService.initialize),
     );
  }
}

// Usage in widgets
class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final container = DependencyProvider.of<RootContainer>(context);
    
    return FutureBuilder<DatabaseService>(
      // Database is initialized only when this widget is built
      future: container.database(),
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {
          return CircularProgressIndicator();
        }
        
        return Text('Database ready: ${snapshot.data?.isConnected}');
      },
    );
  }
}

Benefits of Lazy Initialization:

• Faster App Startup: Dependencies are created only when needed
• Memory Optimization: Unused services don't consume memory
• Flexible Initialization: You can control when heavy operations are performed
• Simple API: Easy to use with both sync and async dependencies

Codecov