Preventing Cursor Move when Validation Fails - ios

Question

I would like to implement validation in my view such that, when the user enters invalid text into a UITextField, all other UITextFields are disabled and the cursor remains in the current place. I am using the SwiftValidator library (https://github.com/jpotts18/SwiftValidator).
The validation of a text field is triggered by UIControlEvent.EditingDidEnd, which typically happens when the user moves to the next field. I have not been able to prevent the cursor moving to the other UITextField nor have I been able to get it back to the view that failed validation. What would be the right approach?
Below are the relevant sections of my code, where validateSingleValue() is the place where I'm trying to implement the logic for this task.
My ViewController acts as a delegate to my custom control groups, handling EditingDidEnd events. The custom controls are typically a UILabel and a UITextField embedded in a UIView.
func textViewEditingDidEnd(editTextPropertyGroup: EditTextPropertyGroup) {
validateField(editTextPropertyGroup.propertyValue)
}
Fields are validated using
func validateField(sender: AnyObject) {
switch (sender as! UITextField) {
case firstNameField:
validateSingleValue(textfield: firstNameField, validationrule: firstNameRule(), errorlabel: firstNameErrorLabel, container: firstNameField.superview)
case lastNameField:
validateSingleValue(textfield: lastNameField, validationrule: lastNameRule(), errorlabel: lastNameErrorLabel, container: lastNameField.superview)
case adressField:
validateSingleValue(textfield: addressField, validationrule: addressRule(), errorlabel: addressErrorLabel, container: addressField.superview)
case emailField:
validateSingleValue(textfield: emailField, validationrule: emailRule(), errorlabel: emailErrorLabel, container: emailField.superview)
default:
print("No fields to validate.")
}
}
func validateSingleValue(textfield textField:UITextField, validationrule validationRule: Rule, errorlabel errorLabel: UILabel, container: UIView?) -> Bool {
if validationRule.validate(textField.text!) {
errorLabel.hidden = true
textField.layer.borderColor = UIColor.grayColor().CGColor
textField.layer.borderWidth = 0.5
enableAllControls()
return true
} else {
errorLabel.hidden = false
textField.layer.borderColor = UIColor.redColor().CGColor
textField.layer.borderWidth = 1.0
if let unwrappedContainer = container {
textField.becomeFirstResponder()
disableAllControls()
unwrappedContainer.userInteractionEnabled = true
unwrappedContainer.alpha = 1.0
}
return false
}
}
and for disabling and enabling the controls:
override func disableAllControls() {
self.FirstNameSection.propertyValue.userInteractionEnabled = false
self.FirstNameSection.alpha = 0.3
self.LastNameSection.userInteractionEnabled = false
self.LastNameSection.alpha = 0.3
self.AddressSection.userInteractionEnabled = false
self.AddressSection.alpha = 0.3
self.EmailSection.userInteractionEnabled = false
self.EmailSection.alpha = 0.3
}
override func enableAllControls() {
self.FirstNameSection.propertyValue.userInteractionEnabled = true
self.FirstNameSection.alpha = 1.0
self.LastNameSection.userInteractionEnabled = true
self.LastNameSection.alpha = 1.0
self.AddressSection.userInteractionEnabled = true
self.AddressSection.alpha = 1.0
self.EmailSection.userInteractionEnabled = true
self.EmailSection.alpha = 1.0
}

Answer 1

Jerry, I did something like this many moons ago; this is a snippet of the code in objective C I fear, sorry.
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
if ([textField.accessibilityIdentifier isEqualToString:#"ClassSize"]) {
if ([self isNumeric:string]) {
return YES;
} else {
return NO;
}
}
return YES;
}
Basically if the user tried to input incorrect data, the keyboard didn't respond.
I used this technique to guard agains't number that were beyond a certain range and indeed even to restrict said user when entering a hexadecimal number I recall. They could only enter 0-F in the field.

Answer 2

It turns out that all this can be achieved with only a few lines of code. To support validation, the UITextFieldDelegate protocol defines the following methods:
textFieldShouldBeginEditing(_:)
textFieldDidBeginEditing(_:)
textFieldShouldEndEditing(_:)
textFieldDidEndEditing(_:)
(see documentation here)
The code in the question can be reduced to:
var shouldEndEdit: Bool = true
func textFieldShouldEndEditing(textField: UITextField) -> Bool {
validator.validateField(textField) { error in
if error == nil {
self.shouldEndEdit = true
} else {
self.shouldEndEdit = false
}
}
return self.shouldEndEdit
}
plus the validation rules as described here.