The package aims to improve a code organization and a visual clarity with Strategy Template.
Features
StgContext
Container for dependencies, that must be provided to any Strategy, can contain a payload and can be created with timeout, after expiration of it Strategy will not be executed.
Strategy
Function, which will be executed after occurring event, that it can handle
StrategyMixin
Provides functionality to handle events with Strategies
Usage
1. Setup controller
Add the mixin to your favorite state controller, specify type of an event which will trigger the state changing
class ContactsBloc extends Bloc<ContactsEvent, ContactsState>
with StrategyMixin<ContactsEvent> {
ContactsBloc() : super(InitialContactsState()) {
on<ContactsEvent>((event, emit) async {
final ctx = await invoke(event);
emit(ctx.find<ContactsState>('state'));
});
}
Don't forget to include the 'invoke(event);' function, without it, the controller will not be able to understand what to do
2. Implement your Strategy, add a business logic to it
class SelectUser implements Strategy {
const SelectUser();
Future<StgContext> _(StgContext ctx) async {
final user = ctx.find<SelectUserEvent>('event').selected;
final prevState = ctx.find<ContactsState>('state');
final prevSelected = [...prevState.selectedUsers];
final newState = UsersSelectedState(
users: prevState.users, selectedUsers: prevSelected..add(user));
return Future.value(ctx..inject('state', newState));
}
@override
Future<StgContext> call(StgContext ctx) async {
if (!ctx.expired) {
return await _(ctx);
} else {
throw Exception(
'[$runtimeType Error] Tried to invoke the strategy after timeout, please handle this case');
}
}
}
3. Override 'strategies' property of the mixin
@override
final Map<Type, Strategy> strategies = const <Type, Strategy>{
LoadDataEvent: LoadTasksAndUsers(),
SelectUserEvent: SelectUser(),
DeselectUserEvent: DeselectUser(),
};
For full example, go to the repo (/example folder).