uitextfield控制输入长度

self.accountTextField=[[UITextField alloc]initWithFrame:CGRectMake(26, CGRectGetMaxY(self.titleLabel.frame)+6, bgView.frame.size.width-52, 38)];
[self.accountTextField setFont:[UIFont systemFontOfSize:14]];
[self.accountTextField setBorderStyle:UITextBorderStyleRoundedRect];
[self.accountTextField setPlaceholder:@"请输入昵称"];
[self.accountTextField addTarget:self action:@selector(editChange:) forControlEvents:UIControlEventEditingChanged];
[self.accountTextField setClearButtonMode:UITextFieldViewModeAlways];
[bgView addSubview:self.accountTextField];

- (void)editChange:(UITextField*)textfield {
 NSString *toBeString = textfield.text;
 NSString *lang = [[UIApplication sharedApplication]textInputMode].primaryLanguage; 
  if ([lang isEqualToString:@"zh-Hans"]) {
         // 简体中文输入，包括简体拼音，健体五笔，简体手写
     UITextRange *selectedRange = [textfield markedTextRange];
      //获取高亮部分
        UITextPosition *position = [textfield positionFromPosition:selectedRange.start offset:0];
      // 没有高亮选择的字，则对已输入的文字进行字数统计和限制
       if (!position) {
            if (toBeString.length > kMaxLength)
          {
                NSRange rangeIndex = [toBeString rangeOfComposedCharacterSequenceAtIndex:kMaxLength];
              if (rangeIndex.length == 1)
             {
                    textfield.text = [toBeString substringToIndex:kMaxLength];
               }
                else
                {
                    NSRange rangeRange = [toBeString rangeOfComposedCharacterSequencesForRange:NSMakeRange(0, kMaxLength)];
                  textfield.text = [toBeString substringWithRange:rangeRange];
             }
            }
        }
    }
// 中文输入法以外的直接对其统计限制即可，不考虑其他语种情况
 else{
       if (toBeString.length > kMaxLength)
      {
            NSRange rangeIndex = [toBeString rangeOfComposedCharacterSequenceAtIndex:kMaxLength];
          if (rangeIndex.length == 1)
         {
                textfield.text = [toBeString substringToIndex:kMaxLength];
           }
            else
            {
                NSRange rangeRange = [toBeString rangeOfComposedCharacterSequencesForRange:NSMakeRange(0,kMaxLength)];
               textfield.text = [toBeString substringWithRange:rangeRange];
         }
        }
    }

}