In flutter, we can declare a function as variable and call it like this
MyWidget((){print('HI');});
class MyWidget extends StatelessWidget{
final Function sayHi;
MyWidget(this.sayHi);
@override
Widget build(BuildContext context) {
sayHi();
return ...
}
}
But what if sayHi() is a async function? How to declare a async function as variable? There seems no class like AsyncFunction. So how to achive that?
Async functions are normal functions with some sugar on top. Here, the function variable type just needs to specify that it returns a Future:
class Example {
Future<void> Function() asyncFuncVar;
Future<void> asyncFunc() async => print('Do async stuff...');
Example() {
asyncFuncVar = asyncFunc;
asyncFuncVar().then((_) => print('Hello'));
}
}
void main() => Example();
Hope this helps.
Like this
class MyApp extends StatelessWidget {
void asyncFunc() async {
await Future.delayed(Duration(seconds: 5));
print('printed after 5 seconds');
}
@override
Widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
debugShowCheckedModeBanner: false,
home: Scaffold(
body: Center(
child: MyWidget(asyncFunc),
),
),
);
}
}
class MyWidget extends StatelessWidget {
final void Function() asyncFunc;
const MyWidget(this.asyncFunc);
@override
Widget build(BuildContext context) {
return MaterialButton(
onPressed: asyncFunc,
);
}
}
asyncFunc in MyWidget is not recognized as a async function so I can't use asyncFunc().then(...). Is that possible? Thanks again.