passing a function as a parameter to a regular class in flutter - flutter

Question

I am trying to pass a function to a regular class (not a widget class) in flutter and inside that class, I have a dialog box. I want to call the dialog box and when the user presses a button the function is passed as a parameter that should trigger.
This is my regular class code
import 'package:finsec/core/res/strings.dart';
import 'package:flutter/material.dart';
import '../../../../core/res/text_sizes.dart';
import '../../data/repositories/app_database.dart';
class ShowDialog {
final void Function() onPressCallback;
BuildContext context;
ShowDialog (this.onPressCallback, this.context) ;
Future<String> showMyDialog() async {
return showDialog<String>(
context: context,
barrierDismissible: false, // user must tap button!
builder: (BuildContext context) {
return AlertDialog(
title: const Text('Income Data'),
content: SingleChildScrollView(
child: ListBody(
children: const <Widget>[
Text(
'Do you want to apply these changes for future income transactions?',
style: TextStyle(
fontSize: text_size_18,
),
),
Text(
'\nPress NO if changes are only for this week income. Press Yes to apply changes to future weeks.',
style: TextStyle(
fontSize: text_size_18,
),
),
],
),
),
actions: <Widget>[
TextButton(
onPressed: () {
Navigator.pop(context, successful);
},
child: const Text(cancelButton),
),
TextButton(
onPressed: () {
onPressCallback();
Navigator.pop(context, successful);
},
child: const Text(noButton),
),
TextButton(
onPressed: () {
onPressCallback();
Navigator.pop(context, successful);
},
child: const Text(yesButton),
),
],
);
},
);
}
}
I am calling ShowDialog class like this in my widget class. Below is the function call
CupertinoButton(
padding: EdgeInsets.zero,
onPressed: () async {
await ShowDialog(
await database.deleteIncomeData(transaction),
context,
);
},
),
My code is working but not as expected. When I pass my function as a parameter, the database.deleteIncomeData(transaction) executes immediately and my showMyDialog() function in ShowDialog class doesn't get called. When I pass a function as a parameter to ShowDialog class, I don't want the function to execute immediately. I want my dialog box function to be called and show a dialog box. When the user presses a button on the dialog box, then the function parameter should execute.
Can someone help me how to modify my code to accomplish what I described above? Thanks in advance!

Answer 1

I recommend learning more about Future and async/await.
Be careful, because your class ShowDialog is waiting for two parameters, one is a Function and the other is the context.
There are some errors in this line
await ShowDialog(
await database.deleteIncomeData(transaction),
context,
);
First, you don't need to await because here you are calling the constructor. You have to call the showMyDialog method.
await ShowDialog(
await database.deleteIncomeData(transaction),
context,
).showMyDialog();
So, in that case, you will have something to await. The result of showMyDialog.
And the second one is that you are not passing a Function to the constructor, you are passing the value that await database.deleteIncomeData(transaction) returns.
(Unless the value that returns is a Function, in that case, it is ok)
And to fix that you have to pass a Function that calls database.deleteIncomeData(transaction)
await ShowDialog(
() => await database.deleteIncomeData(transaction),
context,
).showMyDialog();