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;
}