Limiting input

April 28th, 2011

A common scenario in iOS development is to create a textfield that will only allow a certain number of characters to be entered. We can implement this constraint by:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
    BOOL validCharactersInRange = YES;
    if (![string isEqualToString:@""]) 
        NSUInteger testLength = textField.text.length + string.length + range.length;
        validCharactersInRange = (testLength > 1) ? NO : YES; //change the 1 to your textfield's upper limit
    return validCharactersInRange;

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