UITextField在输入时限制中文输入的长度

- (BOOL)textField:(UITextField*)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString*)string {

    UITextRange*selectedRange = [textFieldmarkedTextRange];

   //获取高亮部分

    UITextPosition*position = [textFieldpositionFromPosition:selectedRange.startoffset:0];

    NSString* str =@"";

    if(selectedRange){

        str = [textFieldtextInRange:selectedRange];

    }

    if([stringisEqualToString:@""])

        returnYES;

    if(position) {//有高亮

        if(range.length==0) {//还在输入

            if(textField.text.length- str.length>=_limitCount) {

                NSString* toBestring = [textField.textstringByReplacingCharactersInRange:rangewithString:str];

                toBestring = [toBestringsubstringWithRange:[toBestring rangeOfComposedCharacterSequencesForRange:NSMakeRange(0, _limitCount)]];;;

                self.alertInput.text= toBestring;

                [selfzt_showHint:[NSStringstringWithFormat:@"最多%ld字符",_limitCount] yOffset:-200];

                returnNO;

            }else{

                returnYES;

            }

        }else{//选中键盘上的中文

            NSString* toBestring = [textField.textstringByReplacingCharactersInRange:rangewithString:string];

            if(toBestring.length>_limitCount) {

                toBestring = [toBestringsubstringWithRange:[toBestring rangeOfComposedCharacterSequencesForRange:NSMakeRange(0, _limitCount)]];;;

                self.alertInput.text= toBestring;

                [selfzt_showHint:[NSStringstringWithFormat:@"最多%ld字符",_limitCount] yOffset:-200];

                returnNO;

            }

            returnYES;

        }

    }else{//没高亮

        if((textField.text.length+ string.length) >_limitCount){

            [selfzt_showHint:[NSStringstringWithFormat:@"最多%ld字符",_limitCount] yOffset:-200];

            returnNO;

        }

    }

    return YES;

}