Force lowercase - ios swift - ios

Question

I would like to force lowercase in an UITextfield when the user is typing.
I came out so far with this code, but seems like it's not lowering characters.
func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
if string.characters.count == 0 {
return true
}
let currentText = textField.text ?? ""
let prospectiveText = (currentText as NSString).stringByReplacingCharactersInRange(range, withString: string.lowercaseString)
switch textField {
// Allow only lower-case vowels in this field,
// and limit its contents to a maximum of 6 characters.
case userNameTextField:
return prospectiveText.characters.count <= 27
default:
return true
}
}

Answer 1

First you should set following property on your textfield to restrict auto capitalisation:
textfield.autocapitalizationType = UITextAutocapitalizationType.None
And this is how you can restrict it further:
func textField(textField: UITextField!, shouldChangeCharactersInRange range: NSRange, replacementString string: String!) -> Bool {
if let _ = string.rangeOfCharacterFromSet(NSCharacterSet.uppercaseLetterCharacterSet()) {
// Do not allow upper case letters
return false
}
return true
}
UPDATED FOR SWIFT 4
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
if let _ = string.rangeOfCharacter(from: .uppercaseLetters) {
// Do not allow upper case letters
return false
}
return true
}

Answer 2

You could do like this and lowercase the entire string when something has changed.
textfield.addTarget(self, action: "textViewChanged", forControlEvents: .EditingChanged);
func textViewChanged(){
textfield.text = textfield.text?.lowercaseString;
}

Answer 3

for swift 3 users, the above code given by Abhinav is just converted to the following
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
if let _ = string.rangeOfCharacter(from:NSCharacterSet.uppercaseLetters) {
return false
}
return true
}

Answer 4

if you want to convert all input characters to lower case you should do this code:
Swift 4:
in override func viewDidLoad() add this:
textfield.addTarget(self, action: #selector(self.textFieldDidChange(_:)), for: UIControlEvents.editingChanged)
and then add this function to your class:
#objc func textFieldDidChange(_ textField: UITextField) {
if let text:String = textfield.text {
DispatchQueue.main.async {
self.textfield.text = text.lowercased()
}
}
}
it is necessary to change it in main thread.