how to not allowed spaces in text field - swift

Question

this is my code I want the user name not to have spaces and lowercase
example (wizkhalifa)
func textField(_ textFieldToChange: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
if textFieldToChange == username {
let characterSetNotAllowed = CharacterSet.whitespaces
if let _ = string.rangeOfCharacter(from:NSCharacterSet.uppercaseLetters) {
return false
}
if let _ = string.rangeOfCharacter(from: characterSetNotAllowed, options: .caseInsensitive) {
return false
} else {
return true
}
}
if UserNameField.text != nil, emailField.text != nil, passwordField.text != nil, rePassword.text != nil && passwordField.text == rePassword.text {
Auth.auth().createUser(withEmail: emailField.text!, password: passwordField.text!, completion: { (user, error) in
if error != nil {
AlertController.showAlert(self, titel: "Error", message: " Fill all fields \nUser exists ")
return
}

Answer 1

You need to check 2 things and you can put that check in the method called when trying to create a user, and/or when the user is typing.
First check, spaces :
if let text = UserNameField.text {
if text.components(separatedBy: " ").count > 1 && text.lowercased() != textField.text {// add your other tests on this line
// the text is in lowercase without space character and your tests pass
Auth.auth().createUser(withEmail: emailField.text!, password: passwordField.text!, completion: { (user, error) in
// check if there is an error
})
} else {
AlertController.showAlert(self, titel: "Error", message: " Fill all fields \nUser exists ")
}
Here is the version for OP with his code :
if UserNameField.text != nil, emailField.text != nil, passwordField.text != nil, rePassword.text != nil && passwordField.text == rePassword.text && UserNameField.text.components(separatedBy: " ").count <= 1 && UserNameField.text.lowercased() == UserNameField.text {
Auth.auth().createUser(withEmail: emailField.text!, password: passwordField.text!, completion: { (user, error) in
if error != nil {
AlertController.showAlert(self, title: "Error", message: " Fill all fields \nUser exists ")
return
} else {
// all good
}
})
} else {
AlertController.showAlert(self, title: "Error", message: " Fill all fields \nUser exists ")
}