(Experimental) Unidirectional data-flow State management for Dart humbly inspired by ngrx <= Redux <= Elm, André Stalz work & Parsley.
- Redarx with Flutter example (uses [built_value])
- Redarx with AngularDart example
- Redarx with Vanilla Dart example
Goal : decouple request from action. View only dispatch dumb requests, the logic to execute the request is delegated to a command.
final requestMap =
<RequestType, CommandBuilder<TodoModel>>{
RequestType.ADD_TODO: AddTodoCommand.constructor(),
RequestType.UPDATE_TODO: UpdateTodoCommand.constructor(),
RequestType.CLEAR_ARCHIVES: ClearArchivesCommand.constructor(),
RequestType.COMPLETE_ALL: CompleteAllCommand.constructor(),
RequestType.LOAD_ALL: AsyncLoadAllCommand.constructor(DATA_PATH),
RequestType.TOGGLE_SHOW_COMPLETED: ToggleShowArchivesCommand.constructor()
};
final config = new CommanderConfig<RequestType>(requestMap);
final store = new Store<TodoModel>(() => new TodoModel.empty());
final dispatcher = new Dispatcher();
final cmder = new Commander(config, store, dispatcher.onRequest);
Flutter
final requestMap = <RequestType, CommandBuilder>{
RequestType.LOAD_ALL: AsyncLoadAllCommand.constructor(DATA_PATH),
RequestType.ADD_TODO: AddTodoCommand.constructor(),
RequestType.UPDATE_TODO: UpdateTodoCommand.constructor(),
RequestType.CLEAR_ARCHIVES: ClearArchivesCommand.constructor(),
RequestType.COMPLETE_ALL: CompleteAllCommand.constructor(),
RequestType.TOGGLE_SHOW_COMPLETED: ToggleShowArchivesCommand.constructor()
};
void main() {
runApp(new StoreProvider(requestMap: requestMap, child:new TodoApp()));
}
Vanilla Dart
var app = new AppComponent(querySelector('#app') )
..model$ = store.data$
..dispatch = dispatcher.dispatch
..render();
RequestType are defined via an enum
enum RequestType {
ADD_TODO,
UPDATE_TODO,
ARCHIVE,
CLEAR_ARCHIVES,
TOGGLE_SHOW_COMPLETED
}
// you can enforce the typing by creating an optionnal request class
class TodoRequest<T extends Todo> extends Request<RequestType, T> {
TodoRequest.loadAll() : super(RequestType.LOAD_ALL);
TodoRequest.clearArchives() : super(RequestType.CLEAR_ARCHIVES);
TodoRequest.completeAll() : super(RequestType.COMPLETE_ALL);
TodoRequest.toggleStatusFilter() : super(RequestType.TOGGLE_SHOW_COMPLETED);
TodoRequest.add(T todo) : super(RequestType.ADD_TODO, withData: todo);
TodoRequest.cancel(T todo) : super(RequestType.CANCEL_TODO, withData: todo);
TodoRequest.update(T todo) : super(RequestType.UPDATE_TODO, withData: todo);
}
Requests are defined by a type and an optional payload.
dispatch( new TodoRequest.add(new Todo(fldTodo.value)));
or
Requests are mapped to commands by Commander and passed to the store.update()
exec(Request a) {
store.update(config[a.type](a.payload));
}
The commands define a public exec method which receive the currentState and return the new one.
class AddTodoCommand extends Command<TodoModel> {
Todo todo;
AddTodoCommand(this.todo);
@override
TodoModel exec(TodoModel model) => model..items.add(todo);
static CommandBuilder constructor() {
return (Todo todo) => new AddTodoCommand(todo);
}
}
Async commands allows async evaluation of the new state
Basically a (stream<Command<Model>>) => stream<Model>
transformer
Receives new commands, and executes those with the current state/Model
Use a CommandStreamReducer<S extends Command, T extends AbstractModel>
to stream reduced states
The store manage a stream of immutable states instances.
The reversible store keep a history list of all executed commands and allow cancelling.
it provide an access to currentState by reducing all the commands history.
The store exposes a stream of immutable states
Stream<TodoModel> _model$;
set model$(Stream<TodoModel> value) {
_model$ = value;
modelSub = _model$.listen((TodoModel model) {
list.todos = model.todos;
footer.numCompleted = model.numCompleted;
footer.numRemaining = model.numRemaining;
footer.showCompleted = model.showCompleted;
});
}
Async commands are maybe not the best way to connect a Firebase data-source.
The redarx_ng_firebase example shows a way to dispatch firebase queries via a new dispatcher method : query.
Queries are dispatched to a Firebase service, which update the base. The service handles firebase.database child and values events and dispatch update request via the dispatch() method.
The Application State is managed in a Store.
State is updated by commands, and the store keep a list of executed commands.
State is evaluated by commands updates,
In reversible-store, cancellation is allowed by simply remove the last command from "history".
A Commander listen to a stream of Requests dispatched by a Dispatcher injected in the application components | controllers | PM | VM
Each Request is defined by an RequestType enum, and can contains data.
Requests are "converted" to commands by the Commander, based on the CommanderConfig.map definition
-
the dispatcher.dispatch function is injected in view || controller || PresentationModel || ViewModel
-
Request are categorized by types, types are defined in RequestType enum
-
the dispatcher stream Requests
-
the dispatcher requestStream is injected in Commander, the commander listen to it, transforms Request to Command and transfer to the store.apply( command ) method
-
each Request is tied to a command via a CommanderConfig which is injected in Commander
// instanciate commands form requests
config[request.type](request.payload);
- Commander need a CommanderConfig containing a Map<RequestType,CommandBuilder>
- the store then execute commandHistory and push the new model value to a model stream
-
fix the generic/command ( mess) -
implements a Scan stream transformer » to allow only run the last commands & emit the last reduced state -
async commands -
test Angular integration -
test with Firebase -
typed Request ? BookRequest, UserRequest ...? => TodoRequest cf. flutter example -
use values types cf built_value
-
multiple stores ?
-
time travel / history UI
-
tests
-
external config file ?
-
...
- use a EnumClass implementation rather than dart enum type
- dispatcher : use a streamController.add rather than dispatch method ?
- multiple store ? dispatcher ? commander ?
- each component could set an Request stream and the commander could maybe listen to it
- study Dart : streams, generics, annotations, asynchrony...
- study Redux & ngrx, play with reducers & Request/Commands mapping...
- and more studies, more experiments, more play...
- define a solid architecture for my coming projects