不错的判断 UITextView 内容不超过20个字符串的方法

 - (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{

     if ([text isEqualToString:@"\n"]){
         [self onSendBarrage:nil];
         return YES;
     }
     NSMutableAttributedString *attrM = [[NSMutableAttributedString alloc]initWithAttributedString:textView.attributedText];
     if (textView == self.textFieldBarrage)
     {
         if (attrM.length > MAX_INPUT_LEN) {
             NSRange range = NSMakeRange(, MAX_INPUT_LEN);
             textView.attributedText = [attrM attributedSubstringFromRange:range];
         }
         [self fixChatButtonStateWithTextViewLength:attrM.length];
     }
     return YES;
 }

以上代码的好处主要在于,先提前计算用户输入的内容,再根据推断出的输入框结果,对输入框的字符进行截取.