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a simple yet powerful state management technique for Flutter

States_rebuilder

pub package actions workflow codecov

Code CleanPerformance
• Separation of UI & business logic◦ Support for immutable / mutable state
• Coding business logic in pure Dart◦ Predictable and controllable
• Zero Boilerplate without code-generation     ◦ Strictly rebuild control
User-friendlyEffective Production
◦ Elegant and lightweight syntax• Super easy for CRUD development
SetState & Animation in StatelessWidget• User authentication and authorization
◦ Navigation without BuildContext• App themes, multi-langs management
◦ Built-in dependency injection system• Easy to test, mock the dependencies

Table of Contents

Although states_rebuilder is a feature-rich library, the maintenance cost is very low, and the size of the library is small. this is because states_rebuilder does not draw a single pixel on the screen and the way the internal code is structured makes adding new functionality a straightforward process with fewer lines of code.


Getting Started with States_rebuilder #

  1. Install this package:
  • With Flutter:
 flutter pub add states_rebuilder
  • Or: add into your pubspec.yaml:
  dependencies:
    states_rebuilder: ... 
  1. Import it in any Dart code:
import 'package:states_rebuilder/states_rebuilder.dart';
  1. Basic use case:
/* -------------  🗄️ Plain Data Class ------------- */
class Counter {
  final int value;
  Counter(this.value);
  
  @override
  String toString() => 'Counter($value)';
}

/* --------------  🤔 Business Logic -------------- */
//🚀 These states are immutable
@immutable
class ViewModel {
  // Inject a reactive state of type int.
  // Works for all primitives, List, Map and Set
  final counter1 = 0.inj();

  // For non primitives and for more options
  final counter2 = RM.inject<Counter>(
    () => Counter(0),
    // State will be redone and undone
    undoStackLength: 8,
    // Build-in logger
    debugPrintWhenNotifiedPreMessage: 'counter2',
  );

  //A getter that uses the state of the injected counters
  int get sum => counter1.state + counter2.state.value;

  incrementCounter1() {
    counter1.state++;
  }

  incrementCounter2() {
    counter2.state = Counter(counter2.state.value + 1);
  }
}

/* ------------------- 👍 Setup ------------------- */
/// 🚀 As [ViewModel] is immutable and final, it is safe to globally instantiate it.
// The state of counter1 and counter2 will be auto-disposed when no longer in use.
// NOTE: They are testable and mockable.

// States inject like this have global scope and can be reached from anywhere.
final viewModel = ViewModel();
// To create many independent instances of viewModel and inject them into the widget 
// tree using the concept of InheritedWidget, see the section on global and local 
// state below.

/* --------------------  👀 UI -------------------- */
///🚀 Just use [ReactiveStatelessWidget] widget instead of StatelessWidget.
// CounterApp will automatically register in any state consumed in its widget child 
// branch, regardless of its depth, provided the widget is not lazily loaded as 
// in the builder method of the ListView.builder widget. 

// BTW, if you're looking for optimization for rebuild by target widget, 
// check out [OnReactive] or [OnBuilder].
class CounterApp extends ReactiveStatelessWidget {
  const CounterApp();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
          children: [
            Counter1View(), // Not const to make it rebuildable
            const Counter2View(), // Notice the use of const modifier (good approach)
            Text('🏁 Result: ${viewModel.sum}'), // Will be updated when sum changes
          ],
        ),
      ),
    );
  }
}

// Child 1 - Plain StatelessWidget
class Counter1View extends StatelessWidget {
  const Counter1View({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        ElevatedButton(
          child: const Text('🏎️ Counter1 ++'),
          onPressed: () => viewModel.incrementCounter1(),
        ),
        // Listen to the state from parent
        Text('Counter1 value: ${viewModel.counter1.state}'),
      ],
    );
  }
}

// Child 2 - User ReactiveStatelessWidget because Counter2View 
// is instantiated with const modifier
class Counter2View extends ReactiveStatelessWidget {
  const Counter2View({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        ElevatedButton(
          child: const Text('🏎️ Counter2 ++'),
          onPressed: () => viewModel.incrementCounter2(),
        ),
        ElevatedButton(
          child: const Text('⏱️ Undo'),
          onPressed: () => viewModel.counter2.undoState(),
        ),
        Text('Counter2 value: ${viewModel.counter2.state.value}'),
      ],
    );
  }
}

Breaking Changes #

Breaking VersionSupportLink
5.0✅ Least versionDoc
4.0Legacy (2021-09-30)Doc
3.0Legacy (2020-09-04)Doc
2.0Legacy (2020-06-02)Doc

Use of modern version is recommended for getting maximum performance & development experience with flutter 2.0.


A Quick Tour of states_rebuilder APIs #

Business logic and state injection #

The specificity of states_rebuilder is that it has practically no boilerplate. It has no boilerplate to the point where you do not have to monitor the asynchronous state yourself. You do not need to add fields to hold for example onLoading, onLoaded, onError states. states_rebuilder automatically manages these asynchronous statuses and exposes the isIdle,isWaiting, hasError andhasData getters and onIdle, onWaiting, onError and onData hooks for use in the user interface logic. In addition you have the full control on which state status to ignore.

With states_rebuilder, you write business logic without bearing in mind how the user interface would interact with it.


This is a typical simple business logic class:

class Foo { // Don't extend any other library specific class
  int mutableState = 0; // The state can be mutable 
  final int immutableState; // Or it can be immutable (no difference)
  Foo(this.immutableState);

  Future<int> fetchSomeThing async(){
    // No need for any kind of async state tracking variables
    return repository.fetchSomeThing();
    // No need for any kind of notification
  }

  Stream<int> streamSomeThing async*(){
    // Methods can return stream, future, or simple sync objects,
    // states_rebuilder treats them equally
  }
}

To make the Foo object reactive, we simply inject it using global functional injection:

final Injected<Foo> foo = RM.inject<Foo>(
  ()=> Foo(),
  onInitialized : (Foo state) => print('Initialized'),
  // Default callbacks for side effects.
  sideEffects: SideEffects(
    onSetState: (snap){
      snap.onAll(
        onIdle: () => print('Is idle'),
        onWaiting: () => print('Is waiting'),
        onError: (error) => print('Has error'),
        onData: (Foo data) => print('Has data'),
      );
    },
    // It is disposed when no longer needed
    dispose: ()=>  print('Disposed'),
  ),
  // To persist the state
  persist:() => PersistState(
      key: '__FooKey__',
      toJson: (Foo s) => s.toJson(),
      fromJson: (String json) => Foo.fromJson(json),
      // Optionally, throttle the state persistance
      throttleDelay: 1000,
  ),

  // stateInterceptor as a middleWare place
  // It can also be used to return another state created 
  // from the current state and the next state.
  stateInterceptor: (currentSnap, nextSnap) {
    // Example of simple email validation
    if (nextSnap.hasData) {
      if (!nextSnap.data.contains('@')) {
        return nextSnap.copyToHasError(
          Exception('Enter a valid Email'),
        );
      }
    }
  },
);

// A handy syntax, injection you can use `.inj()` extension:
final foo = Foo().inj();
final isBool = false.inj();
final string = 'str'.inj();
final count = 0.inj();
final trueOrNull = null.inj<bool?>();

Injected interface is a wrapper class that encloses the state we want to inject. The state can be mutable or immutable.

Injected state can be instantiated globally or as a member of classes. They can be instantiated inside the build method without losing the state after rebuilds.

To inject a state, you use RM.inject, RM.injectFuture, RM.injectStream or RM.injectFlavor.

The injected state even if it is injected globally, it has a lifecycle. It is created when first used and destroyed when no longer used. Between the creation and the destruction of the state, it can be listened to and mutated to notify its registered listeners.

When the state is disposed of, its list of listeners is cleared, and if the state is waiting for a Future or subscribed to a Stream, it will cancel them to free resources.

Injected state can depend on other Injected states and recalculate its state and notify its listeners whenever any of its Inject model that it depends on emits a notification.

🔍 See more detailed information about the RM.injected API.

State change and notification #

To mutate the state and notify to listener(s):

// Set state synchronously 
foo.state = newFoo;

// Set state asynchronously 
foo.stateAsync = repository.fetchSomeThing();

// For more options
foo.setState(
  (s) => s.fetchSomeThing(),
  // Run `side-effect` during setState
  sideEffects: SideEffects.onWaiting(()=> showSnackBar()),
  stateInterceptor: (currentSnap, nextSnap){
    // 
  }
  debounceDelay : 400,
);

// For boolean type state
foo.toggle();

The state when mutated emits a notification to its registered listeners. The emitted notification has a boolean flag to describe is status :

  • isIdle : the state was first created and no notification has been emitted yet.
  • isWaiting: the state is waiting for an async task to end.
  • hasError: the state mutation has ended with an error.
  • hasData: the state mutation has ended with valid data.
  • isActive: the state had data at least one time.

Typically when executing any async task the state changes form isWaiting to hasData or hasError. In some use cases we are interested on skipping some of the stages. This can be done using stateInterceptor parameter.

// For more options
foo.setState(
  (s) => s.fetchSomeThing(),
  // stateInterceptor is called after new state calculation and just 
  // before state mutation. It exposes the current and the next snapState.
  stateInterceptor: (currentSnap, nextSnap){
    // Ignoring the waiting stage.
    if(nextSnap.isWaiting) return currentSnap;
  }
);

🔍 See more detailed information about setState API.

You can notify listeners without changing the state using :

foo.notify();

You can also refresh the state to its initial state and reinvoke the creation function then notify listeners using:

foo.refresh();

refresh is useful to re-execute async data fetching to get the updated data from a server. Typical use is the refresh a ListView display.

If the state is persisted, calling refresh will delete the persisted state and replace it with the newly created one.

Calling refresh will cancel any pending async task from the state before refreshing.

🔍 See more detailed information about the refresh API.

State subscription and Reactive Builders #

There are to for get your widget rebuilds by state:

Widget BuildersStyleLink
OnReactive, ReactiveStatelessWidget👩🏻‍💻 By defaultFinish him!
OnBuilder👨🏻‍🚒 Strictly rebuilds by targetGet Over Here!

OnReactive widget and ReactiveStatelessWidget #

To listen to an injected state and rebuild a part of the widget tree, just wrap that part of the widget tree inside OnReactive widget:

final counter1 = RM.inject<int>(()=> 0) // Equivalent to 0.inj();
final counter2 = 0.inj();          // Or: using extension style

int get sum => counter1.state + counter2.state;

// In the widget tree:
Column(
    children: [
        OnReactive( // Will listen to counter1
            ()=> Text('${counter1.state}');
        ),
        OnReactive( // Will listen to counter2
            ()=> Text('${counter2.state}');
        ),
        OnReactive( // Will listen to both counter1 and counter2
            ()=> Text('$sum');
        )
    ]
)

Inside OnReactive you can call any of the available state status flags (isWaiting, hasError, hasData, ...) or just simply use onAll and onOrElse methods:

// Option 1: I do it by myself! 😤
OnReactive(
    ()=> {
        if(myModel.isWaiting){
            return WaitingWidget();
        }
        if(myModel.hasError){
            return ErrorWidget();
        }
        return DataWidget();
    }
)
// Option 2: use onAll method:   (defined all status)
OnReactive(
    ()=> myModel.onAll(
            onWaiting: ()=> WaitingWidget(),
            onError: (err, refreshErr)=> ErrorWidget(),
            onData: (data)=> DataWidget(),
        );
)

// Option 3: use onOrElse method: (expected or undefined status)
OnReactive(
    ()=> myModel.onOrElse(
            onData: (data)=> DataWidget(),
            orElse: ()=> IndicatorWidget(),
        );
)

Similar to OnReactive widget there is the abstract widget ReactiveStatelessWidget. When the ReactiveStatelessWidget is used instead of StatelessWidget, the widget becomes reactive and implicitly tracks its listeners in the widget tree they are provided that the widget such as inside the builder method of the ListView.builder widget:

class MyWidget extends ReactiveStatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
          Text('${counter1.state}'),
          Text('${counter2.state}'),
          Text('$sum'),
      ]
    );
  }
}

LIMITATION:

ReactiveStatelessWidget andOnReactive cannot update const widgets, widgets inside thebuilder of ListView.builder and widgets insideSlivers.

OnReactive(
  ()=> Column(
     children: [
       // const will not update
       const _Widget(), 
       Expanded(
         child: ListView.builder(
           itemCount: 1,
           itemBuilder: (context, index) {
             // Inside builder will not register to OnReactive
             // To make it reactive wrap it with OnReactive
             return _Widget(); 
           },
         ),
       ),
       Expanded(
         child: CustomScrollView(
           slivers: [
             SliverAppBar(
               // Inside SliverAppBar will not register to OnReactive
              // To make it reactive wrap it with OnReactive
               title: _Widget(), 
             ),
             SliverList(
               delegate: SliverChildListDelegate(
                 [
                   // Inside SliverList will not register to OnReactive
                   // To make it reactive wrap it with OnReactive
                   _Widget(), 
                 ],
               ),
             ),
             SliverGrid(
               gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                 crossAxisCount: 1,
               ),
               delegate: SliverChildBuilderDelegate(
                   (BuildContext context, int index) {
                     // Inside SliverChildBuilderDelegate will not register to OnReactive
                     // To make it reactive wrap it with OnReactive
                     return _Widget();  
                   },
               ),
             ),
           ],
         ),
       ),
     ],
  ),
);

OnBuilder widget #

In most cases OnReactive do the job. Nevertheless, if you want to explicitly specify the listeners you want to listen to, use OnBuilder widget.

OnBuilder(
    listenTo: myState,
    // Called whenever myState emits a notification
    builder: () => Text('${counter.state}'),
    sideEffects: SideEffects(
        initState: () => print('initState'),
        onSetState: (snapState) => print('onSetState'),
        onAfterBuild: () => print('onAfterBuild'),
        dispose: () => print('dispose'),
    ),
    shouldRebuild: (oldSnap, newSnap) {
      return true;
    },
    debugPrintWhenRebuild: 'myState',
),

If you want to listen to many injected states use listenToMany parameter.

In this case onBuilder will react to a combined state of all injected states.

OnBuilder.all(
    listenToMany: [myState1, myState2],
    onWaiting: () => Text('onWaiting'), // Will be invoked if at least one state is waiting
    onError: (err, refreshError) => Text('onError'), // Will be invoked if at least on state has error
    onData: (data) => Text(myState.state.toString()), // Will be invoked if all states have data.
),

All onError callbacks expose a refresher. It can be used to refresh the error; that is recalling the last function that caused the error.

If you want to optimize widget rebuild and prevent some part of the child widget tree from unnecessary rebuilding, use Child, Child2, Child3 widget.

Child(
  (child) => OnReactive(
      () => Colum(
          children: [
              Text('model.state'), // This part will rebuild
              child, // This part will not rebuild
          ],
      ),
  ),
  child: WidgetNotToRebuild(),
);

You can make your state widget-wise and override it to present different branches of the widget tree.

final items = [1,2,3];

final item = RM.inject(()=>null);

class App extends StatelessWidget{
  build (context){
    return ListView.builder(
      itemCount: items.length,
      itemBuilder: (BuildContext context, int index) {
        return item.inherited( // Inherited uses the `InheritedWidget` concept
          stateOverride: () => items[index],
          builder: () {

            return const ItemWidget();
            // Inside ItemWidget you can use the buildContext to get 
            // the right state for each widget branch using:

            // This Element owner of context is registered to item model.
            item.of(context);

            // Or: this Element owner of context is not registered to item model.
            item(context); 
          }
        );
      },
    );
  }
}

Global and local state #

State can be injected globally or scoped locally.

Scoped locally means that the state's flow is encapsulated withing the widget and its children. If more than one widget is created, each has its own independent state.

Global state #

  //In the global scope
  final myState = RM.inject(() => MyState())

// Or Encapsulate it inside a business logic class (BLOC):

  //For the sake of best practice, one strives to make the class immutable
  @immutable
  class MyBloc {  // or MyViewModel, or MyController
    final _myState1 = RM.inject(() => MyState1())
    final _myState2 = RM.inject(() => MyState2())
    //Other logic that mutate _myState1 and _myState2
  }
  //As MyBloc is immutable, it is safe to instantiate it globally
  final myBloc = MyBloc();

Local state (Scoped state) #

If the state or the Bloc are configurable (parametrized), Just declare them globally and override the state in the widget tree.

  // The state will be initialized in the widget tree.
  final myState = RM.inject(() => throw UnimplementedError())
  // In the widget tree
  myState.inherited(
    stateOverride: () {
      return MyState(parm1,param2);
    },
    builder: (context) {
      // Read the state through the context
      final _myState = myState.of(context);
    }
  )

Similar with Blocs

  final myBloc = RM.inject<MyBloc>(() => throw UnimplementedError())
  //In the widget tree
  myState.inherited(
    stateOverride: () {
      return MyBloc(parm1, param2);
    },
    builder: (context) {
      final _myBloc = myBloc.of(context);
    }
  )

State persistence #

To Persist the state and retrieve it when the app restarts,

  final model = RM.inject<MyModel>(
      ()=>MyModel(),
    persist:() => PersistState(
      key: 'modelKey',
      toJson: (MyModel s) => s.toJson(),
      fromJson: (String json) => MyModel.fromJson(json),
      // Optionally, throttle the state persistance
      throttleDelay: 1000,
    ),
  );

You can manually persist or delete the state

  model.persistState();
  model.deletePersistState();

Undo and redo immutable state #

Note: you should first set undoStackLength: from RM.inject

  model.undoState();
  model.redoState();

🔍 See more detailed information about undo redo state.


Route management #

To use Navigator version 2,

   final InjectedNavigator myNavigator = RM.injectNavigator(
     // Define your routes map
     routes: {
       '/': (RouteData data) => Home(),
        // redirect all paths that starts with '/home' to '/' path
       '/home/*': (RouteData data) => data.redirectTo('/'),
       '/page1': (RouteData data) => Page1(),
       '/page1/page11': (RouteData data) => Page11(),
       '/page2/:id': (RouteData data) {
         // Extract path parameters from dynamic links
         final id = data.pathParams['id'];
         // OR inside Page2 you can use `context.routeData.pathParams['id']`
         return Page2(id: id);
        },
       '/page3/:kind(all|popular|favorite)': (RouteData data) {
         // Use custom regular expression
         final kind = data.pathParams['kind'];
         return Page3(kind: kind);
        },
       '/page4': (RouteData data) {
         // Extract query parameters from links
         // Ex link is `/page4?age=4`
         final age = data.queryParams['age'];
         // OR inside Page4 you can use `context.routeData.queryParams['age']`
         return Page4(age: age);
        },
        // Using sub routes
        '/page5': (RouteData data) => RouteWidget(
              builder: (Widget routerOutlet) {
                return MyParentWidget(
                  child: routerOutlet;
                  // OR inside MyParentWidget you can use `context.routerOutlet`
                )
              },
              routes: {
                '/': (RouteData data) => Page5(),
                '/page51': (RouteData data) => Page51(),
              },
            ),
     },
     //
     // Called after a location is resolved and just before navigation.
     // It is used for route guarding and global redirection.
     onNavigate: (RouteData data) {
       final toLocation = data.location;
       if (toLocation == '/homePage' && userIsNotSigned) {
         return data.redirectTo('/signInPage');
       }
       if (toLocation == '/signInPage' && userIsSigned) {
         return data.redirectTo('/homePage');
       }
     
       //You can also check query or path parameters
       if (data.queryParams['userId'] == '1') {
         return data.redirectTo('/superUserPage');
       }
     },
     //
     // Called when route is going back.
     // It is used to prevent leaving pages before date is validated
     onNavigateBack: (RouteData data) {
       if(data== null){
         // data is null when the back Button of Android device is hit and the route 
         // stack is empty.

         // returning true we will exit the app.
         // returning false we will stay on the app.
         return false;
       }
       final backFrom = data.location;
       if (backFrom == '/SingInFormPage' && formIsNotSaved) {
         RM.navigate.toDialog(
           AlertDialog(
             content: Text('The form is not saved yet! Do you want to exit?'),
             actions: [
               ElevatedButton(
                 onPressed: () => RM.navigate.forceBack(),
                 child: Text('Yes'),
               ),
               ElevatedButton(
                 onPressed: () => RM.navigate.back(),
                 child: Text('No'),
               ),
             ],
           ),
         );
 
         return false;
       }
     },
   );

In the widget tree, use MaterialApp.router widget:

  class MyApp extends StatelessWidget {
     const MyApp({Key? key}) : super(key: key);
 
     @override
     Widget build(BuildContext context) {
       return MaterialApp.router(
         routeInformationParser: myNavigator.routeInformationParser,
         routerDelegate: myNavigator.routerDelegate,
       );
     }
   }

To navigate imperatively:

  myNavigator.to('/page1');
  myNavigator.toDeeply('/page1');
  myNavigator.toReplacement('/page1', argument: 'myArgument');
  myNavigator.toAndRemoveUntil('/page1', queryParam: {'id':'1'});
  myNavigator.back();
  myNavigator.backUntil('/page1');

To navigate declaratively:

  myNavigator.setRouteStack(
    (pages){
      // exposes a copy of the current route stack
      return [...newPagesList];
    }
  )

To navigate to pageless routes, show dialogs and snackBars without BuildContext:

  myNavigator.toPageless(HomePage());
  RM.navigate.toDialog(AlertDialog( ... ));
  RM.scaffoldShow.snackbar(SnackBar( ... ));

InjectedNavigator is a reactive model so you can listen to it using ReactiveStatelessWidget:

  @override
  Widget build(BuildContext context) {
    return OnReactive(
      () => Text('${context.routeData.location}'),
    );
  }

You can easily change page transition animation, using one of the predefined TransitionBuilder or just define yours.


Create, Read, Update and Delete items from backend service #

  • To Create, Read, Update and Delete (CRUD) from backend or DataBase,

    final products = RM.injectCRUD<Product, Param>(
        ()=> MyProductRepository(), // Implements ICRUD<Product, Param>
        readOnInitialization: true, // Optional (Default is false)
    );
    
    // READ
    products.crud.read(param: (param)=> NewParam());
    // CREATE
    products.crud.create(NewProduct());
    // UPDATE
    products.crud.update(
      where: (product) => product.id == 1,
      set: (product)=> product.copyWith(...),
    );
    // DELETE
    products.crud.delete(
      where: (product) => product.id == 1,
      isOptimistic: false, // Optional (Default is true)
    );
    

Authentication and authorization #

To authenticate and authorize users,

  final user = RM.injectAuth<User?, Param>(
      ()=> MyAuthRepository(),// Implements IAuth<User?, Param>
      autoRefreshTokenOrSignOut: (user)=> Duration(seconds: user.tokenExpiryDate)
  );
  // in the widget tree
  OnAuthBuilder(
    listenTo: user,
    onUnsigned: ()=> LoginPage(),
    onSigned: ()=> UserHomePage(),
  )
  // later on: 
  // Sign up
  user.auth.signUp((param)=> Param());
  // Sign in
  user.auth.signIn((param)=> Param());
  // Sign out
  user.auth.signOut();

Dynamic theme switching #

To dynamically switch themes,

  final theme = RM.injectTheme<String>(
      lightThemes : {
        'simple': ThemeData.light( ... ),
        'solarized': ThemeData.light( ...),
      },
      darkThemes: {
        'simple': ThemeData.dark( ... ),
        'solarized': ThemeData.dark( ...),
      };
      themeMode: ThemeMode.system;
      persistKey: '__theme__',
  );
  // Choose the theme
  theme.state = 'solarized'
  // Toggle between dark and light mode of the chosen them
  theme.toggle();

App internationalization and localization #

To internationalize and localize your app:

  // U.S. English
  class EnUS {
    final helloWorld = 'Hello world';
  }
  // Spanish
  class EsEs implements EnUs{
    final helloWorld = 'Hola Mondo';
  }

You can use json or arb file for language translations.

  final i18n = RM.injectI18N<EnUS>(
      {
        Local('en', 'US'): ()=> EnUS(); // Can be async
        Local('es', 'ES'): ()=> EsES();
      };
      persistKey: '__lang__', // Local persistance of language 
  );

In the UI:

  Text(i18n.of(context).helloWorld);
  // Choose the language
  i18n.locale = Local('es', 'Es');
  // Or: choose the system language
  i18n.locale = SystemLocale();

Animation in StatelessWidget #

Implicit and explicit animation #

  final animation = RM.injectAnimation(
    duration: const Duration(seconds: 1),
    curve: Curves.linear,
  );

In the UI: For Implicit animation

  Center(
    child: OnAnimationBuilder(
        listenTo: animation,
        builder: (animate) => Container(
            // Animate is a callable class
            width: animate.call(selected ? 200.0 : 100.0),
            height: animate(selected ? 100.0 : 200.0, 'height'),
            color: animate(selected ? Colors.red : Colors.blue),
            alignment: animate(selected ? Alignment.center : AlignmentDirectional.topCenter),
            child: const FlutterLogo(size: 75),
        ),
    ),
  ),

For explicit animation

  OnAnimationBuilder(
    listenTo: animation,
    builder: (animate) => Transform.rotate(
    angle: animate.formTween(
        (currentValue) => Tween(begin: 0, end: 2 * 3.14),
    )!,
    child: const FlutterLogo(size: 75),
    ),
  ),

Working with TextFields and Form validation #

To deal with TextFields and Form validation

  final email =  RM.injectTextEditing():

  final password = RM.injectTextEditing(
    validators: [
      (String? value) {
        if (value!.length < 6) {
          return "Password must have at least 6 characters";
        }
        return null;
      },
    ],
  );

    final acceptLicence = RM.injectedFormField(
    validators: [
      (bool? value) {
        if (bool != true) {
          return "You have to accept the licence";
        }
        return null;
      },
    ],
  );

  final form = RM.injectForm(
    autovalidateMode: AutovalidateMode.disable,
    autoFocusOnFirstError: true,
    submit: () async {
      // This is the default submission logic:
      //  1. it may be override when calling form.submit( () async { });
      //  2. it may contains server validation.
      await serverError =  authRepository.signInWithEmailAndPassword(
          email: email.text,
          password: password.text,
        );
        // After server validation
        if(serverError == 'Invalid-Email'){
          email.error = 'Invalid email';
        }
        if(serverError == 'Weak-Password'){
          email.error = 'Password must have more the 6 characters';
        }
    },
    onSubmitting: () {
      // Called while waiting for form submission,
    },
    onSubmitted: () {
      // Called after form is successfully submitted
      // for example: navigation to user page
    }
  );

In the UI:

    OnFormBuilder(
      listenTo: form,
      builder: () => Column(
        children: <Widget>[
            TextField(
                focusNode: email.focusNode,
                controller: email.controller,
                decoration: InputDecoration(
                  errorText: email.error,
                ),
                onSubmitted: (_) {
                  // Request the password node
                  password.focusNode.requestFocus();
                },
            ),
            TextField(
                focusNode: password.focusNode,
                controller: password.controller,
                decoration: new InputDecoration(
                  errorText: password.error,
                ),
                onSubmitted: (_) {
                  // Request the submit button node
                  form.submitFocusNode.requestFocus();
                },
            ),
            OnFormFieldBuilder<bool>(
              listenTo: acceptLicence,
              builder: (value, onChanged){
                return CheckBoxListTile(
                  value: value,
                  onChanged: onChanged,
                  title: Text('Do you accept the licence?'),
                )
              }
            ),
            OnFormSubmissionBuilder(
              listenTo: form,
              onSubmitting: () => CircularProgressIndicator(),
              child : ElevatedButton(
                focusNode: form.submitFocusNode,
                onPressed: (){
                    form.submit();
                },
                child: Text('Submit'),
              ),
            ),     
        ],
      ),
  ),

Working with scrollable view #

  • To work with scrolling list:

    final scroll = RM.injectScrolling(
      initialScrollOffset: 0.0,
      keepScrollOffset: true,
      endScrollDelay: 300,
      onScrolling: (scroll){
        if (scroll.hasReachedMinExtent) {
          print('Scrolling vertical list is in its top position');
        }
        if (scroll.hasReachedMaxExtent) {
          print('Scrolling vertical list is in its bottom position');
        }
    
        if (scroll.hasStartedScrolling) {
          // Called only one time.
          print('User has just start scrolling');
        }
      }
    );
    

    In the UI:

    ListView(
        controller: scroll.controller, // Ready to go 🏃‍♀️ 🏃
        children: <Widget>[],
    );
    
  • 🔍 See more detailed information about InjectedScrolling.

Working with page and tab views #

  • To work with tabs and page views:

      final injectedTab = RM.injectTabPageView(
        initialIndex: 2,
        length: 5,
      );
    

    In the UI: with the same injectedTab you can control TabBarView, PageView, TabBar and BottomNavigationBar.

      Widget build(BuildContext context) {
        return MaterialApp(
          home: Scaffold(
            body: Column(
              children: [
                Expanded(
                  child: OnTabPageViewBuilder(
                    builder: (index) {
                      return TabBarView(
                        controller: injectedTab.tabController,
                        children: views,
                      );
                    },
                  ),
                ),
                Expanded(
                  child: OnTabPageViewBuilder(
                    builder: (index) {
                      return PageView(
                        controller: injectedTab.pageController,
                        children: pages,
                      );
                    },
                  ),
                )
              ],
            ),
            bottomNavigationBar: OnTabPageViewBuilder(
              listenTo: injectedTab,
              builder: (index) => BottomNavigationBar(
                currentIndex: index,
                onTap: (int index) {
                  injectedTab.index = index;
                },
                selectedItemColor: Colors.blue,
                unselectedItemColor: Colors.blue[100],
                items: tabs
                    .map(
                      (e) => BottomNavigationBarItem(
                        icon: e,
                        label: '$index',
                      ),
                    )
                    .toList(),
              ),
           ),
          ),
        );
    
  • 🔍 See more detailed information about InjectedTabPageView.

  • Here are many show cases of tabs and pages.

Test and injected state mocking #

All Injected state can be mocked for test. To mock it in test:

    model.injectMock(()=> MyMockModel());
    model.injectFutureMock(()=> MyMockModel());
    products.injectCRUDMock(()=> MockRepository())
    user.injectAuthMock(()=> MockAuthRepository())

And many more features.


Examples #

With these series of examples you'll learn the core concepts of state_rebuilder using simple simple and incremental examples.

State management concepts #

Get the foundation of state management from very basic to more advanced concepts

Devolvement booster #

Based on state management principles and some good programing principles and abstraction techniques, I created dedication injected state to automatize the most repetitive tasks a developer do.

Question & Suggestion #

  • Each example is a seed for a tutorial. It would be very encouraging if you wrote one.
  • Please feel free to post an issue or PR, as always, your feedback makes this library become better and better.
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a simple yet powerful state management technique for Flutter

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License

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Dependencies

collection, flutter, flutter_localizations, meta

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