UITextView限制文本长度

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{    NSString *toBeString=[textView.text stringByReplacingCharactersInRange:range withString:text];    if (123 == textView.tag) {        if (range.location>50) {            textView.text = [toBeString substringToIndex:50];            return NO;        }    }    return YES;}- (BOOL)textViewShouldEndEditing:(UITextView *)textView{    if (123 == textView.tag) {        NSString *toBeString = [textView.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];        if (toBeString.length > 50) {            textView.text = [toBeString substringToIndex:50];            return NO;        }    }    return YES;}