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

{

if(textField?==?self.titleField)?{

if(string.length?==?0)returnYES;

NSInteger?existedLength?=?textField.text.length;

NSInteger?selectedLength?=?range.length;

NSInteger?replaceLength?=?string.length;

if(existedLength?-?selectedLength?+?replaceLength?>?20)?{

returnNO;

}

}

returnYES;

}