StringValidator class
The StringValidator class validates that the length of a String is within a specified range between minLength and maxLength.
class StringValidator extends WidgetValidator {
/**
* Maximum length for a valid String. A value of null means this property
* is ignored. It is equals null by default.
*/
int maxLength;
/**
* Error message when the String is longer than the [maxLength] property. By
* default it's equals "This string is longer than the maximum allowed length.
* This must be less than {0} characters long."
*/
String tooLongError = "This string is longer than the maximum allowed length. This must be less than {maxLength} characters long.";
/**
* Minimum length for a valid String. A value of NaN means this property
* is ignored. It is equals null by default.
*/
int minLength;
/**
* Error message when the string is shorter than the [minLength] property. By
* default it's equals "This string is shorter than the minimum allowed length.
* This must be at least {0} characters long."
*/
String tooShortError = "This string is shorter than the minimum allowed length. This must be at least {minLength} characters long.";
StringValidator(Widget widget, {this.maxLength:null, this.minLength:null}) : super(widget);
/**
* Executes the validation logic of this validator, including validating that
* a missing or empty [value] causes a validation error as defined by the
* value of the [required] property. For an invalid result returns an List of
* [ValidationResult] objects, with one ValidationResult object for each
* field examined by the validator that failed validation.
*
* You must override this method in a subclass of a validator class.
*/
List<ValidationResult> doValidation(dynamic value) {
List<ValidationResult> results = super.doValidation(value);
// Return if there are errors or if the required property is set to false
// and length is 0.
String val = value != null ? value.toString() : "";
if (results.length > 0 || ((val.length == 0) && !required))
return results;
else
return _validateString(value);
}
/**
* Validate [value] and return List of [ValidationResult] objects, with one
* ValidationResult object for each field examined by the validator.
*/
List<ValidationResult> _validateString(dynamic value) {
List<ValidationResult> results = [];
String val = value != null ? value.toString() : "";
if (maxLength != null && val.length > maxLength) {
results.add(new ValidationResult(true, substitute(tooLongError, '{maxLength}', maxLength)));
} else if (minLength != null && val.length < minLength) {
results.add(new ValidationResult(true, substitute(tooShortError, '{minLength}', minLength)));
}
return results;
}
}
Extends
Validator > WidgetValidator > StringValidator
Properties
bool enabled #
Property to enable/disable validation process.
Setting this value to false will stop the validator from performing validation. When a validator is disabled, it dispatches no events, and the validate method returns ValidationEvent.VALID instance.
bool enabled = true
List<ValidationListener> listeners #
List of ValidationListener's
List<ValidationListener> listeners = new List<ValidationListener>()
int maxLength #
Maximum length for a valid String. A value of null means this property is ignored. It is equals null by default.
int maxLength
int minLength #
Minimum length for a valid String. A value of NaN means this property is ignored. It is equals null by default.
int minLength
OnInvalid onInvalid #
Callback function invokes when result of validation is invalid.
OnInvalid onInvalid
OnValid onValid #
Callback function invokes when result of validation is valid.
OnValid onValid
bool required #
If true specifies that a missing or empty value causes a validation error.
bool required = true
String requiredError #
Error message when a value is missing and the required property is true.
By default equals "This field is required."
String requiredError = "This field is required."
String tooLongError #
Error message when the String is longer than the maxLength property. By default it's equals "This string is longer than the maximum allowed length. This must be less than {0} characters long."
String tooLongError = "This string is longer than the maximum allowed length. This must be less than {maxLength} characters long."
String tooShortError #
Error message when the string is shorter than the minLength property. By default it's equals "This string is shorter than the minimum allowed length. This must be at least {0} characters long."
String tooShortError = "This string is shorter than the minimum allowed length. This must be at least {minLength} characters long."
Methods
List<ValidationResult> doValidation(value) #
Executes the validation logic of this validator, including validating that
a missing or empty
value causes a validation error as defined by the
value of the required property. For an invalid result returns an List of
ValidationResult objects, with one ValidationResult object for each
field examined by the validator that failed validation.
You must override this method in a subclass of a validator class.
List<ValidationResult> doValidation(dynamic value) {
List<ValidationResult> results = super.doValidation(value);
// Return if there are errors or if the required property is set to false
// and length is 0.
String val = value != null ? value.toString() : "";
if (results.length > 0 || ((val.length == 0) && !required))
return results;
else
return _validateString(value);
}
ValidationEvent validate(value, [bool fireEvent = true]) #
Performs validation of value and notifies the listeners of the result if fireEvent equals true.
ValidationEvent validate(dynamic value, [bool fireEvent = true]) {
ValidationEvent resultEvent;
if (enabled && (value != null || required)) {
// Validate if the target is required or our value is non-null.
resultEvent = _processValidation(value);
} else {
// We assume if value is null and required is false that
// validation was successful.
resultEvent = new ValidationEvent(ValidationEvent.VALID);
}
// Send notification to listeners
if (fireEvent && resultEvent != null) {
listeners.forEach((ValidationListener listener){
listener(resultEvent);
});
}
// Invoke callback validation functions
if (onValid != null && resultEvent.type == ValidationEvent.VALID) {
onValid();
} else if (onInvalid != null && resultEvent.type == ValidationEvent.INVALID) {
onInvalid(resultEvent.results);
}
return resultEvent;
}