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frideos_library sample

An example Todo app created with the frideos library.

Key Concepts

  • This example aims to implement the BLoC pattern in a slightly different way, trying to reduce the amount of code and complexity of the original implementation, making it a little bit easier to adopt by beginners.
  • A singleton instance of the AppState class implementing the AppStateModel interface, holds the state of the app, here is where the only two BLoCs TodosBloc and StatsBloc are instantiated.
  • The state of the app is provided to the widgets tree by the AppStateProvider, a StatefulWidget that uses an InheritedWidget to make possible for the widgets of the subtree to access the data.
  • Instead of one BLoC per screen, in this sample a single BLoC, TodosBloc, contains the business logic of the screens that share similar needs (HomeScreen, DetailScreen and AddEditScreen).
  • To send data from the TodosBloc to the StatsBloc, in order to calculate the number of active and completed todos, it is used the send method of the ListSender class. First, in the TodosBloc is created an instance of the ListSender class, then by its method setReceiver, in the AppState class is set a reference to the stream on the StatsBloc that will receive the todos list whenever the method send is called. In this case, there is no need for the two BLoCs to share the same source of data, or having to pass the TodosBloc as a parameter to the StatsBloc to get the todos list.

UI and Streams

  • As per the classic BLoC implementation, the widgets, most of which in this sample are Stateless, are automatically rebuilt whenever the streams emit a new event.
  • Every time a new value is set, the ValueBuilder widget, which takes as a parameter an object implementing the StreamedObject interface of the library, rebuilds providing the updated data. This is just a widget that extends the StreamBuilder and adds some callbacks to handle the stream state and return a Container if no widget is passed to the NoDataChild parameter, in order to avoid to check for the snapshot.hasData property to not return a null widget, ultimately, resulting in a less and cleaner code.

Testing

There are no particular tricks for testing the app with this library. The sample was tested with unit tests that check for every feature of the apps, and by the integration test with flutter drive.