[swift] How to check if a text field is empty or not in swift

use this extension

extension String {
    func isBlankOrEmpty() -> Bool {

      // Check empty string
      if self.isEmpty {
          return true
      }
      // Trim and check empty string
      return (self.trimmingCharacters(in: .whitespaces) == "")
   }
}

like so

// Disable the Save button if the text field is empty.
let text = nameTextField.text ?? ""
saveButton.isEnabled = !text.isBlankOrEmpty()