How to extract TextFormField as reusable widget in flutter - flutter

Question

I want to make my flutter project highly manageable, apply clean code and maintain DRY concept strictly. There are a lot of input elements in any flutter project. So I want to make this element as a separate widget so that if I want to change in future then I will change in one place. Here is my approach:
import 'package:flutter/material.dart';
import '../utility/validatation.dart';
class RegistrationPage extends StatefulWidget {
static const String routeName = '/registrationPage';
#override
State<RegistrationPage> createState() => _RegistrationPageState();
}
class _RegistrationPageState extends State<RegistrationPage> {
final _formKey = GlobalKey<FormState>();
final TextEditingController nameInput = TextEditingController();
final TextEditingController businessName = TextEditingController();
final TextEditingController productTypeId = TextEditingController();
#override
Widget build(BuildContext context) {
return Scaffold(
body: new Form(
key: _formKey,
autovalidateMode: AutovalidateMode.onUserInteraction,
child: Column(mainAxisAlignment: MainAxisAlignment.center, children: [
Container(
height: 70,
margin: EdgeInsets.only(bottom: 50),
child: Image(image: AssetImage('assets/logo.png')),
),
Padding(
padding: const EdgeInsets.symmetric(vertical: 10, horizontal: 30.0),
child: TextInput(inputController: nameInput, label: 'আপনার নাম'),
),
ElevatedButton(
onPressed: () {
if (_formKey.currentState!.validate()) {
_register(context);
}
},
child: Text('Next'),
)
]),
),
);
}
void _register(BuildContext context) {}
}
class TextInput extends StatelessWidget {
const TextInput({
Key? key,
required this.inputController,
required this.label,
}) : super(key: key);
final TextEditingController inputController;
final String label;
#override
Widget build(BuildContext context) {
return TextFormField(
controller: inputController,
keyboardType: TextInputType.text,
decoration: const InputDecoration(
border: UnderlineInputBorder(),
prefixIcon: Icon(Icons.phone),
labelText: label,
),
validator: (value) {
return Validation.required(value);
},
);
}
}
But I got this error:
What is wrong in my code? Is there any problem in my approach or should I stop thinking to refactor my code as I do? Please also suggest if there is any smarter way to make code more clean and manageable.

Answer 1

Oh I see so you have this
class TextInput extends StatelessWidget {
const TextInput({
Key? key,
required this.inputController,
required this.label,
}) : super(key: key);
final TextEditingController inputController;
final String label;
#override
Widget build(BuildContext context) {
return TextFormField(
controller: inputController,
keyboardType: TextInputType.text,
// Notice the const here right?
// So the idea is that decoration objects could rebuild to either change one thing or the other, so 'label' here cannot be a constant
//So to solve this InputDecoration should not have const.
decoration: const InputDecoration(
border: UnderlineInputBorder(),
prefixIcon: Icon(Icons.phone),
labelText: label,
),
validator: (value) {
return Validation.required(value);
},
);
}
}

Answer 2

Since you are using a variable in InputDecoration, you should not declare InputDecoration with const keyword.