UITextField輸入到最大限值以後不能刪除

轉自：http://blog.csdn.net/linkai5696/article/details/5742421

解決UITextField輸入到最大值不能刪除的現象：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    BOOL isAllowEdit = YES;
    if([string length]>range.length&&[textField.text length]+[string length]-range.length>_NAME_MAX_LENGTH_)
    {
        [textField resignFirstResponder];
        isAllowEdit = NO;
    }
    return isAllowEdit;
}