onChange method
Implementation
void onChange(String d) async {
cont!.value = TextEditingValue(
text: widget.model.value.toString(),
selection: TextSelection(
baseOffset: 0, extentOffset: widget.model.value.toString().length));
if (oldValue != widget.model.value) {
// set answer
bool ok = await widget.model.answer(widget.model.value);
// fire on change event
if (ok == true && mounted) await widget.model.onChange(context);
}
return;
}