validation_notifier

Description:

validation notifier

ValidationNotifier #
A ValueNotifier that validates a value against a collection of customizable rules.
Create a rule
You can create your own set of rules by inheriting ValidationRule<T>
Let's say we create a rule that validates inputs that are required callled RequiredRule
import 'package:validation_notifier/validation_notifier.dart';

class RequiredStringRule extends ValidationRule<String> {
const RequiredStringRule();

@override
String get errorMessage => 'This field is required';

@override
bool checkIsValid(String? value) {
return value?.isNotEmpty ?? false;
}
}
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Another rule that validates string inputs requiring them to have a email format called EmailFormatRule
import 'package:validation_notifier/validation_notifier.dart';

class EmailFormatRule extends ValidationRule<String> {
static final emailRegex = RegExp(
r'^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$');

const EmailFormatRule();

@override
String get errorMessage => 'Invalid email format';

@override
bool checkIsValid(String? value) {
if (value == null) {
return false;
} else {
return RegularExpressions.emailRegex.hasMatch(value);
}
}
}
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Add the rules
You can add your previously created rules to a ValidationNotifier<T>
final email = ValidationNotifier<String>(rules: const [
RequiredRule(),
EmailFormatRule(),
]);
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Use email in a ValueListenableBuilder
ValueListenableBuilder<ValidationResult<String>>(
valueListenable: email,
builder: (context, value, child) {
return TextFormField(
onChanged: email.update,
keyboardType: TextInputType.emailAddress,
autocorrect: false,
decoration: InputDecoration(
labelText: 'Email',
errorText: value.errorMessage,
),
);
},
)
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Call ValidationNotifier<T>.validate() to validate valueToValidate using the rules you defined.
// A callback of a button for logging-in

void onLogin() {
final validationResult = email.validate();

if (evalidationResult.isValid) {
// Valid
} else {
// Invalid
}
}
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Important Notes

When a rule is invalid, ValidationNotifier<T>.value will be set and other calls to remaining rules will be canceled.
The sequence of the rules to be called during validation is determined by the sequence of the rules in ValidationNotifier<T> constructor.