How can I get a textDidChange (like for a UISearchBar) method for a UITextField?

Question

How can I get a textDidChange method for a UITextField? I need to call a method every time a change is made to a text field. Is this possible? Thanks!

Answer 1

Elaborating further on Ben Gottlieb's answer above, using textField shouldChangeCharactersInRange is great but has the disadvantage that some things can happen with a one character delay.

Eg calling the below to alert you when there is no text actually is called the character after, once you have enter a character and it is no longer empty.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    if (!textField.text.length) {
        // Do something with empty textfield
    }
    return YES;
 }

The below method allows you to get a rudimentary change happening in your textField. Although not quite as direct as an NSNotification it still allows you to use similar methods with different textFields and so is a pretty useful thing to use when trying to get specific character changes in your textfield.

The below code fixes the character delay

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    // This means it updates the name immediately
    NSString * newString = [textField.text stringByReplacingCharactersInRange:range withString:string];

    textField.placeholder = newString.length ? @"" : @"Name";

    return YES;
 } 

For this code is used to add a placeholder to a UITextField when there is no text in the textField