//监听UITextField文本变化
[self.textField addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];

- (void) textFieldDidChange:(UITextField *)textField
{
    NSInteger kMaxLength = 10;

    NSString *toBeString = textField.text;

    NSString *lang = [[UIApplication sharedApplication]textInputMode].primaryLanguage; //ios7之前使用[UITextInputMode currentInputMode].primaryLanguage

    if ([lang isEqualToString:@"zh-Hans"]) { //中文输入

        UITextRange *selectedRange = [textField markedTextRange];

        //获取高亮部分
        UITextPosition *position = [textField positionFromPosition:selectedRange.start offset:0];

        if (!position) {// 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 (toBeString.length > kMaxLength) {

                textField.text = [toBeString substringToIndex:kMaxLength];

            }

        } else{//有高亮选择的字符串，则暂不对文字进行统计和限制

        }

    }else{//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

        if (toBeString.length > kMaxLength) {

            textField.text = [toBeString substringToIndex:kMaxLength];

        }

    }

}