Adding TextEditingControllers in a loop in Flutter isn't working - dart

Question

What I try to achieve is for the TextInputField to be autovalidated once there is more than 1 character entered.
Here's my initState (simplified):
#override
void initState() {
autoValidateList.addAll([
_autoValidateEmail,
_autoValidateCompanyName,
_autoValidatePhoneNo,
_autoValidateName,
_autoValidateSurname
]);
textEditingControllersList.addAll([
_emailController,
_companyNameController,
_phoneNoController,
_nameController,
_surnameController
]);
for (int i = 0; i < textEditingControllersList.length; i++) {
TextEditingController controller = textEditingControllersList[i];
controller.addListener(() => () {
print(
'Listener entered. companyName? ${controller == _companyNameController}');
if (controller.text.length > 0) {
print('=> true');
setState(() => autoValidateList[i] = true);
} else {
print('=> false');
setState(() => autoValidateList[i] = false);
}
});
}
_emailController.text = widget.loginData.email;
super.initState();
}
If I add the listeners not in a loop, for example:
_emailController.addListener(() => setState(() {
if (_emailController.text.length > 0) {
_autoValidateEmail = true;
} else {
_autoValidateEmail = false;
}
}));
It works fine.
None of the print statements get executed. What am I missing here?

Answer 1

There's a very insidious error here. Notice that in your addListener, you're passing a function that returns a function. What you want to execute is the function that is being returned, but you're actually executing the function that you're passing.
In a more clear syntax, you're doing this:
controller.addListener(() {
return () {
// Your code
};
});
So, what is happening is:
controller.addListener(() {
print('This is going to be executed');
return () {
print('This is NOT going to be executed. Your code used to be here.');
};
});
Instead of:
controller.addListener(() => () {
...
});
You should be doing:
controller.addListener(() {
...
});
Also, this is not related, but you should be calling super at the beginning of initState, not at the end.