data_widget

data_widget is a Flutter package that provides a simple wrapper for InheritedWidget, InheritedModel, InheritedNotifier, ValueNotifier, and ChangeNotifier.

Features

Data

A widget that holds a single data and allows its descendants to access the data and listen to changes.

Providing the data

Data.inherit(
  data: 'Hello, World!',
  child: const MyWidget(),
)

Getting the data

There are multiple ways to get the data:

Find and listen

This method will find the nearest Data<T> widget (in this case Data<String>). Calling this method will register a listener that will be invoked when the data changes. In other words, the widget will rebuild when the data changes. This will throw an assertion error if the data is not found.

String data = Data.of<String>(context);

Optionally find and listen

This method is similar to Data.of<T>(BuildContext context), but will not throw an assertion error if the data is not found.

String? data = Data.maybeOf<String>(context);

Find

This method will find the nearest Data<T> widget (in this case Data<String>). This will throw an assertion error if the data is not found. This method does not register any listener so the widget will not rebuild when the data changes. This is useful when you only need to read the data once (i.e. in onPressed callback, onTap callback, etc.).

String data = Data.find<String>(context);

Optionally find

This method is similar to Data.find<T>(BuildContext context), but will not throw an assertion error if the data is not found.

String? data = Data.maybeFind<String>(context);

Blocking the data

You can stop the data from being passed down to its descendants by wrapping the widget with Data.boundary

Data.boundary<MyService>(
  child: const MyWidget(),
)

MultiData

A widget that holds multiple data and allows its descendants to access the data and listen to changes without having to nest multiple Data widgets.

Usually, when you need to pass multiple data to its descendants, you will have to nest multiple Data widgets.

Data.inherit(
  data: 'Hello, World!',
  child: Data.inherit(
    data: 42,
    child: Data.boundary<MyService>(
      child: const MyWidget(),
    ),
  ),
)

With MultiData, you can pass multiple data without having to nest multiple Data widgets.

MultiData(
  data: [
    Data<String>('Hello, World!'),
    Data(42), // not providing type is optional, it will be inferred from the data
    Data.boundary<MyService>(), // but a must for boundary
  ],

Getting the data is similar to Data widget.

Note
Providing type in the type param is optional but encouraged to avoid runtime errors due to type mismatch.

Warning
The order of the data must be the same as the order of the data provided.

Model

A widget that holds a single model and allows its descendants to access or change the value of the model. Similar to Data but uses symbol as the key to identify the model. Mostly useful when getting same type data within the same widget tree.

// Using Data
Data.inherit(
  data: 'Hello, World!',
  child: Data.inherit(
    data: 'Another!',
    child: const MyWidget(), // The widget can only access 'Another!' data 
  ),
)
// Using Model
MultiModel(
  data: [
    Model(#myString, 'Hello, World!'),
    Model(#myString2, 'Another!'),
  ],
  child: const MyWidget(), // The widget can access both 'Hello, World!' and 'Another!' data
)

Providing a read-only model

Model.inherit(
  #myString,
  'Hello World',
  child: const MyWidget(),
)

Providing a model

String myString = 'Hello World';

Model.inherit(
  #myString,
  myString,
  child: const MyWidget(),
  onChanged: (value) {
    myString = value;
  },
)

Getting the model

There are multiple ways to get the model, most of them are similar to Data widget.

// Find and listen
String myString = Model.of<String>(context, #myString);
// Optionally find and listen
String? myString = Model.maybeOf<String>(context, #myString);
// Find
String myString = Model.find<String>(context, #myString);
// Optionally find
String? myString = Model.maybeFind<String>(context, #myString);

Blocking the model

You can stop the model from being passed down to its descendants by wrapping the widget with ModelBoundary

/// Single boundary
ModelBoundary<MyService>(
  #myService,
  child: const MyWidget(), // cannot access #myService
)
/// Multiple boundary
MultiModel(
  data: [
    ModelBoundary<MyService>(#myService),
    ModelBoundary<MyService>(#myService2),
  ],
  child: const MyWidget(), // cannot access #myService and #myService2
)

MultiModel

A widget that holds multiple models and allows its descendants to access or change the value of the model. Similar to MultiData but uses symbol as the key to identify the model. Mostly useful when getting same type data within the same widget tree.

MultiModel(
  data: [
    Model(#myString, 'Hello, World!'),
    Model(#myString2, 'Another!'),
    ModelBoundary<MyService>(#myService),
  ],
  child: const MyWidget(),
)

Getting the model is similar to Model widget.

Note
Providing type in the type param is optional but encouraged to avoid runtime errors due to type mismatch.

Warning
The order of the data must be the same as the order of the data provided.

MutableNotifier

When using List (or any mutable object) as the value for ValueNotifier, it will not notify the listeners when the list is mutated, because the reference to the list is not changed. MutableNotifier solves this problem by providing a method to mutate the list and notify the listeners.

MutableNotifier<List<int>> list = MutableNotifier([1, 2, 3]);
list.mutate((value) {
  value.add(4);
});

You can also decide whether to notify the listeners or not.

MutableNotifier<Set<int>> set = MutableNotifier({1, 2, 3});
set.mutate((value) {
  if (!value.contains(4)) {
    value.add(4);
    return true; // notify the listeners
  }
  return false; // do not notify the listeners
});

ValueNotifierUnmodifiableView

A wrapper for ValueNotifier that provides an unmodifiable view of the value.

ValueNotifier<String> valueNotifier = ValueNotifier('Hello, World!');
// Sure you can do this so that the value cannot be changed
ValueListenable<String> castedNotifier = valueNotifier;
// But you can still change the value by casting it back to ValueNotifier
(castedNotifier as ValueNotifier<String>).value = 'Another!';
// This can cause unexpected behavior

// Using ValueNotifierUnmodifiableView
ValueListenable<String> valueListenable = ValueNotifierUnmodifiableView(valueNotifier);
// This prevents the value from being changed outside of your control
(valueListenable as ValueNotifier<String>).value = 'Another!';
// as valueListenable is no longer a ValueNotifier, this will throw an error

You can also use the ValueNotifier extension method to convert the ValueNotifier to ValueNotifierUnmodifiableView.

ValueNotifier<String> _valueNotifier = ValueNotifier('Hello, World!');

ValueListenable<String> get valueListenable => _valueNotifier.readOnly(); 

ValueChangeNotifier

Similar to ValueNotifier, but listeners can be notified with the old value and the new value.

ValueChangeNotifier<int> valueChangeNotifier = ValueChangeNotifier(42);
valueChangeNotifier.addListener((newValue, oldValue) {
  print('Old value: $oldValue');
  print('New value: $newValue');
});
valueChangeNotifier.value = 43;

ListNotifier

A list that can notify the listeners when the list is mutated.

ListNotifier<int> listNotifier = ListNotifier([1, 2, 3]);
listNotifier.addListener((details) {
  print('Added: ${details.added}');
  print('Removed: ${details.removed}');
  print('Index: ${details.index}');  
});
listNotifier.add(4);

SetNotifier

A set that can notify the listeners when the set is mutated.

SetNotifier<int> setNotifier = SetNotifier({1, 2, 3});
setNotifier.addListener((details) {
  print('Added: ${details.added}');
  print('Removed: ${details.removed}');
});
setNotifier.add(4);

MapNotifier

A map that can notify the listeners when the map is mutated.

MapNotifier<int, String> mapNotifier = MapNotifier({1: 'One', 2: 'Two', 3: 'Three'});
mapNotifier.addListener((details) {
  print('Added: ${details.added}'); // added entries
  print('Removed: ${details.removed}'); // removed entries
});
mapNotifier[4] = 'Four';

Getting started

1. Install the package

In your terminal:

flutter pub add data_widget

or you can add it manually in your pubspec.yaml:

dependencies:
  data_widget: {latest_version}

2. Import the package

import 'package:data_widget/data_widget.dart';

Using Experimental Version

If you want to use the experimental version, you can add the following to your pubspec.yaml:

dependencies:
  data_widget:
    git:
      url: "https://github.com/sunarya-thito/data_widget.git"

Libraries

data_widget

extension