The Magical Widget is a package developed in Dart initially for the Flutter framework. It uses BLoC for state management, as recommended by Google, in order to control UI widgets. More specifically, a pattern using the BehaviorSubject is created. In addition, it exploits the functionitlities offered by the source_gen package in order to automatically generate most of the code. Therefore, this library makes it really easy for developper to control their UI widgets with the minimum setup required. Regardless of the level of expertise in Flutter or state management, anyone could now manipulate the widgets with ease.

Getting Started

It is very easy to start using this package, in fact it is boiled down to preperly update your pubspec.yaml file, and to include one single annotation in your code.


First you should update your pubspec.yaml to include the build_runner package under the dev_dependencies key. Also add the magical widget generator package under the same key. For example for build_runner version 1.1.2, and magical_widget_generator version 1.0.0:

  build_runner: ^1.1.2
  magical_widget_generator: ^1.0.0

The last step to finish the pubspec.yaml file is to update your dependencies key and include the main magical widget package that will expose the annotation. In addition, the package makes use of the BLoC state management offered by dart, so you should also include the rxdart package.

  magical_widget: ^1.0.0
  rxdart: ^0.20.0

Using the Annotation

The Magical Widget package is easy to use, and it exposes only one annotation called Alakazam This annotaiton takes one optional parameter called withProvider (default true) and it should be used to annotate an enum in your code. The enum elements should follow this syntax: element_name$element_type$default_value Currently three element types are supported: String, bool, and num In the enum, you are required to specify the element_name, however the last two (element_type and default_value) are optional. If you do not specify the element_type, the default will be String. If you do not specify the default_value, the default settings are:

  • For String, the default value is an empty string
  • For bool, the default value is false
  • For enum, the default is 0 With that being said, an example of using Alakazam:
enum myLoginScreen {

Of course, you should import the magical widget package in order to use this annotation: import 'package:magical_widget/magical_widget.dart';

Generating the Code

After using the annotation as described above on an enum that contains whatever controls you want for your screens, you can now generate the code with build_runner, to do so, you can use

flutter packages pub run build_runner build
// OR
flutter packages pub run build_runner watch

The first build_runner command (build) will generate the source file for you once when you run it, so each time you change the enum, you need to rerun this command. The second command (watch) will generate it once and keep listening to changes in your code, so it will continuously update the generateed code.

Before running the build commands make sure to include part 'your_file_name.g.dart'; at the top of your source file and after your imports.

The generated code makes use of the rxdart package, so make sure to import it in your source file import 'package:rxdart/rxdart.dart';. And if the withProvider parameter of the Alakazam annotation is set to true (default value), the code will generate an inherited widget for you, so you should import the material library import 'package:flutter/material.dart';.

Using the Generated Code

The magical widget package will always generate one enum and two classes. The enum name will be the same as your specified enum name but it will be prefixed by MAGICAL_

The first generated class contains the UI controls defined and initialized to the proper types and values, along side other boilerplate code. The class will always be named MagicalController, and this is the class that will be used with the BLoC, it is the type of the stream. You will never want to use this class explicitly other than referencing it when building a StreamBuilder widget and calling its default constructor MagicalController() if you want to use the initialData argument of the StreamBuilder.

The second generated class is the actual BLoC. It contains the Behavior Subject that will contain a stream of events of the type MagicalController. This class generates all required codes and boilerplates to use the BLoC state management techniques. The class name will always be MagicalBloc. From this class you will be interested to use two properties and two methods:

  1. The magicalValue property that returns the current value of the stream, the returned object is always of type MagicalController
  2. The magicalStream property that returns the actual stream, this will required by the stream argument of the StreamBuilder
  3. The changeUIElement(value, control) method. You want to call this method to change the value of the control (the contol is from the generated enum that starts with MAGICAL_)
  4. The changeUIElements(values, controls) method. Same as above, but it allows to submit a list of values and controls to change at once. The values and controls lists should be of the same size At this point, you can instantiate the MagicalBloc and use the instance in your own inherited widget or provide it as a global parameter for other widgets to use. It depends on your preference, but you are all set to go.

The withProvider Argument

If this argument of the Alakazam annotation is set to true, which is the default behavior, a third class will be generated. The third class is always called MagicalWidget and it is an inherited widget that provides the BLoC to you. So if the withProvider argument is set to true, you can instantly use the MagicalWidget provider to wrap your widgets and use the static of() method to get access to the MagicalBloc instance, which will be always called magicalBloc

In case, you do not want this behavior, you need to explicitly set withProvider to false, then no inherited widget will be generated.


For an example on how to use the magical widget please refer to the example package provided in this github repo.

For a complete tutorial about this package, please refer to this medium article.

You can always refer to the API documentation related to these packages:


Please read for details on our code of conduct, and the process for submitting pull requests.


  • Raef Mousheimish - Initial work - MchRaef

Check the Authors file for more info.


This project is licensed under the MIT License - see the file for details


  • Inspired by the active and motivated Dart and Flutter communities, especially by the built_values package developed by David Morgan