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

You can use the UITextFieldTextDidChangeNotification to call a method whenever the text field changes. Add this to your init :

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textDidChange:) name:UITextFieldTextDidChangeNotification object:nil];

Answer 2

您可以设置委托并使用

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

Answer 3

You can also a target & selector for the UIControlEventEditingChanged event. For example:

[textField addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged]

Note that this will only be called for user initiated changes to the text field and will not be called automatically when programmatically setting text.

Answer 4

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

Answer 5

I found some problem when you use replaceCharactersInRange in delegate shouldChangeCharactersInRange.

Ex: In Vietnamese keyboard string aa -> â , So if you use method replaceCharactersInRange then Incorrect results.

You can try in this case by event UIControlEventEditingChanged :

[textField addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged]

Answer 6

Swift Solution

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

Answer 7

Below is what I used Swift 4

public func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    guard let fieldText = textField.text else {
        return false
    }
    // Append the existing textfield text with the new character
    var text = fieldText + string
    // If it is the very first character, textfield text will be empty so take the 'string' and on delete also textfield text get deleted with a delay
    if range.location == 0{
       text = string
    }
    return true
}

Answer 8

Simply:

class MTextField: NSTextField {
    override func textDidChange(_ notification: Notification) {
        //...
    }
}

In Obj-C (not check):

@interface  MTextField: NSTextField
@end
@implementation  MTextField
- (void) textDidChange:(NSNotification*) notification {
    //...
}
@end