Koin for Flutter

Starting Koin for Flutter

In any Flutter Widget:

void main() {
startKoin((app) {
app.printLogger(level: Level.debug);
app.module(myModule);
});
runApp(MyApp());
}

Flutter Components as KoinComponents

StatefulWidget, are extended by Koin to be considered as KoinComponent out of the box:

class LoginPage extends StatefulWidget {
@override
_LoginPageState createState() => _LoginPageState();
}
class _LoginPageState extends State<LoginPage> {
LoginBloc bloc;
Lazy<LoginBloc> lazyBloc;
@override
void initState() {
// Lazy Inject MyPresenter
lazyBloc = currentScope.inject();
// or directly retrieve instance
bloc = get();
super.initState();
}
@override
Widget build(BuildContext context) {
return Container();
}
}

Those classes can then use:

  • get() or by inject() instance retrieving
  • getKoin() to access th current Koin instance

If you need to inject dependencies from another class and can't declare it in a module, you can still tag it with KoinComponent interface.

Extended Scope API

Scope API is more close to the Flutter platform. The StatefulWidget have extensions for Scope API: currentScope get the current associated Koin scope.

Koin gives the ScopeStateMixin mixin already bound to your Flutter StatefulWidget lifecycle. On dispose() is calld, it will close automatically. ScopeStateMixin overrides the dispose method to call the close method of the current scope.

You can use the ScopeStateMixin in StatefulWidget to close automatically the scope when the widget is removed from the tree. Whenever there is a scope associated with a StatefulWidget you must use the ScopeStateMixin or manually call the currentScope.close" function in the dispose lifecycle widget function.

important

If the ScopeStateMixin is not used and you do not call currentScope.close the instantiated scope for each instance of this Widget will not be closed, that is, the StatefulWidget will be removed from the tree, but the scope associated with it will remain in memory.

You can use directly the associated Koin scope to retrieve components:

Easy to declare your Flutter Widgets's scope:

class LoginPage extends StatefulWidget {
@override
_LoginPageState createState() => _LoginPageState();
}
class _LoginPageState extends State<LoginPage> {
LoginBloc loginBlock;
@override
void initState() {
// or directly retrieve instance
loginBlock = currentScope.get();
super.initState();
}
@override
Widget build(BuildContext context) {
return Container();
}
}
final loginModule = Module()
// Declare a scope to LoginPage
..scope<LoginPage>((s) {
s.scoped((s) => LoginBloc());
});

Any StatefulWidget can use directly the scope API: createScope(), getScope() and deleteScope().

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