How shouldChangeCharactersInRange works in Swift?

Question

I'm using shouldChangeCharactersInRange as a way of using on-the-fly type search.

However I'm having a problem, shouldChangeCharactersInRange gets called before the text field actually updates:

In Objective C, I solved this using using below:

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {     NSString * searchStr = [textField.text stringByReplacingCharactersInRange:range withString:string];      return YES; } 

However, I've tried writing this in Swift:

func textField(textField: UITextField!, shouldChangeCharactersInRange range: NSRange, replacementString string: String!) -> Bool {     let txtAfterUpdate:NSString = self.projectSearchTxtFld.text as NSString     txtAfterUpdate.stringByReplacingCharactersInRange(range, withString: string)      self.callMyMethod(txtAfterUpdate)     return true } 

The method still gets called before I get a value?

Answer 1

Swift 4, Swift 5

This method doesn't use NSString

// MARK: - UITextFieldDelegate  extension MyViewController: UITextFieldDelegate {     func textField(_ textField: UITextField,                    shouldChangeCharactersIn range: NSRange,                    replacementString string: String) -> Bool {         if let text = textField.text,            let textRange = Range(range, in: text) {            let updatedText = text.replacingCharacters(in: textRange,                                                        with: string)            myvalidator(text: updatedText)         }         return true     } } 

Note. Be careful when you use a secured text field.