typedef MyTypedef(int value);

class MyController {
  VoidCallback myFunction;
  VoidCallback mySecondFunction;
  MyTypedef functionThatReturns;

  void dispose() {
    //Remove any data that's will cause a memory leak/render errors in here
    myFunction = null;
    mySecondFunction = null;
    functionThatReturns = null;
  }
}

class MyWidget extends StatefulWidget {
  const MyWidget({this.controller});
  final MyController controller;
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State {
  @override
  void initState() {
    super.initState();
    MyController _controller = widget.controller;
    if (_controller != null) {
      _controller.myFunction = firstFunction;
      _controller.mySecondFunction = secondFunction;
      _controller.functionThatReturns = functionWithInt;
    }
  }

  void firstFunction() {
    print('Calling first function');
  }

  void secondFunction() {
    print('Calling second function');
  }

  void functionWithInt(int value) {
    print('Calling third function with value $value');
  }

  @override
  Widget build(BuildContext context) {
    return Container();
  }
}