how to use validator with two variables in one textformfield? - flutter

Question

I'd like to ask on if there are anyway on how to compare in a conditional statement the two variable. As you can see, couponSalePriceCtrlr and couponOrigPriceCtrlr. I'd like to validate that the user's input in sale price SHOULD not be greater than the original price, but it seems like the validator accepts only the (value) parameter and a String data type.
Widget editCouponSalePriceWidget(couponSalePriceCtrlr, couponOrigPriceCtrlr) {
// converted the variable parameters into double data type
double convertedSalePrice = double.parse(couponSalePriceCtrlr);
double convertedOrigPrice = double.parse(couponOrigPriceCtrlr);
return Padding(
padding: const EdgeInsets.symmetric(horizontal: 0.0),
child: TextFormField(
style: const TextStyle(fontFamily: 'Poppins', fontSize: 13),
controller: couponSalePriceCtrlr,
keyboardType: TextInputType.number,
decoration: InputDecoration(
suffixText: "*",
suffixStyle: TextStyle(color: Colors.red),
labelText: 'Sale Price',
labelStyle: const TextStyle(
fontSize: 15, fontFamily: 'Poppins', color: Color(0xFF152C4C)),
isDense: true,
prefixIcon: const Icon(Icons.person),
enabledBorder: OutlineInputBorder(
borderSide: const BorderSide(color: Color(0xFFCECECE)),
borderRadius: BorderRadius.circular(12),
),
focusedBorder: OutlineInputBorder(
borderRadius: BorderRadius.circular(12),
borderSide: const BorderSide(color: Color(0xFFCECECE)),
),
hintText: 'Orig Price',
fillColor: const Color(0xFFFEFEFE),
filled: true,
),
// however the validator only accepts, a string data type.
validator: (convertedSalePrice,convertedOrigPrice) {
if (convertedSalePrice!.isEmpty ||
!RegExp(r'[0-9]+[,.]{0,1}[0-9]*').hasMatch(convertedSalePrice)) {
return "Please enter a valid original price.";
} else {
return null;
}
},
),
);
}

Answer 1

I assume you have 2 TextFormField, one for original price, another for sale price. Of course it is String type, that's the rule :) Therefore you need to convert it to integer/double type. If your keyboardType is number, it is unnecessary to check user's input is string type, else do it.
TextFormField(
controller: couponOrigPriceCtrlr,
keyboardType: TextInputType.number,
)
TextFormField(
controller: convertedSalePrice,
keyboardType: TextInputType.number,
validator: (saleStr) {
double originalDouble = double.parse(couponOrigPriceCtrlr.text);
double saleDouble = double.parse(saleStr.text);
// check what ever you want here
// ...
}
)