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Description:

form field validator

form_field_validator #
A straightforward flutter form field validator that provides common validation options.
Usage #
// assign it directly to a TextFormField validator
// you don't have the pass the value your self like
// validator: (value) => EmailValidator(errorText: 'invalid email address').call(value)

TextFormField(
validator: EmailValidator(errorText: 'enter a valid email address')
);

// create a reusable instance
final requiredValidator = RequiredValidator(errorText: 'this field is required');

// again assign it directly to the validator
TextFormField(validator: requiredValidator);

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Multi rules validation #

final passwordValidator = MultiValidator([
RequiredValidator(errorText: 'password is required'),
MinLengthValidator(8, errorText: 'password must be at least 8 digits long'),
PatternValidator(r'(?=.*?[#?!@$%^&*-])', errorText: 'passwords must have at least one special character')
]);

String password;

Form(
key: _formKey,
child: Column(children: [
TextFormField(
obscureText: true,
onChanged: (val) => password = val,
// assign the the multi validator to the TextFormField validator
validator: passwordValidator,
),

// using the match validator to confirm password
TextFormField(
validator: (val) => MatchValidator(errorText: 'passwords do not match').validateMatch(val, password),
)
]),
);

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Make your own validator #

class LYDPhoneValidator extends TextFieldValidator {
// pass the error text to the super constructor
LYDPhoneValidator({String errorText = 'enter a valid LYD phone number'}) : super(errorText);

// return false if you want the validator to return error
// message when the value is empty.
@override
bool get ignoreEmptyValues => true;

@override
bool isValid(String value) {
// return true if the value is valid according the your condition
return hasMatch(r'^((+|00)?218|0?)?(9[0-9]{8})$', value);
}
}

// use it by assigning it to the TextFormField validator
TextFormField(validator: LYDPhoneValidator());

// you can also extend the base FieldValidator class
// to work with non string values

class CustomValidator extends FieldValidator<T>{
CustomValidator(String errorText) : super(errorText);

@override
bool isValid(T value) {
// TODO: implement isValid
return //condition;
}
}

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