Is it possible to specify type of `onQtyChanged` ?

[pmatatias]

Currently I used ValueChanged?, which the function will return dynmic. even use InputQty.int the value actually int but the parameter of the onQtyChanged is dynamic value.

I had do some experiment by declare inside constructor. but then i can call it inside state class. Please take a look at this question on Stakoverflow: https://stackoverflow.com/q/77158813/12838877

My experiment can found on branch update-onChange :
https://github.com/pmatatias/input-quantity/tree/update-onChange