How to pass generic provider to child?

Question

I want to create a universal alert that I will use several times in my app.

class SelectIconAlertDialogWidget extends StatelessWidget {
  const SelectIconAlertDialogWidget({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    final model = Provider.of<IncomeViewModel>(context, listen: true).state;

    return AlertDialog(
      shape: RoundedRectangleBorder(
        borderRadius: BorderRadius.circular(40),
      ),

Problem is that I can not figure out how to pass type of parent ChangeNotifier

                  showDialog<String>(
                    context: context,
                    builder: (_) =>
                        ChangeNotifierProvider<IncomeViewModel>.value(
                      value: view,
                      child: const SelectIconAlertDialogWidget(),
                    ),
                  );

I have a lot of ViewModels that will use this alert so dont want to repeat this code and write generic Alert that I can use with any ViewModel. How can I achieve this?

Answer 1

Create some abstract class with methods or fields you want to have for all your view models you use for that dialog

abstract class AbstractViewModel{
  void doStuff();
}

Implement this class for your view models

class MyViewModel1 implements AbstractViewModel{
   @override
   void doStuff (){ print("from MyViewModel1");}
}

Add type parameter for your dialog class

 class SelectIconAlertDialogWidget<T extends AbstractViewModel> extends StatelessWidget {
  const SelectIconAlertDialogWidget({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    // and you can use generic type T like this:
    final model = Provider.of<T>(context, listen: true);
    model.doStuff();

    return AlertDialog(
      shape: RoundedRectangleBorder(
        borderRadius: BorderRadius.circular(40),
      ),

And call it passing type parameter SelectIconAlertDialogWidget<MyViewModel1>()

showDialog<String>(
                    context: context,
                    builder: (_) =>
                        ChangeNotifierProvider<MyViewModel1>.value(
                      value: view,
                      child: const SelectIconAlertDialogWidget<MyViewModel1>(),
                    ),
                  );

On build method of your dialog widget it will print "from MyViewModel1". Hope you got the concept of abstraction.