判断用户输入的银行卡号是否正确的方法(基于Luhn算法的格式校验)

/** * 银行卡格式校验 * * @param cardNo 银行卡号 * * @return  */+ (BOOL) checkCardNo:(NSString*) cardNo{      int oddsum = 0;   //奇数求和  int evensum = 0;  //偶数求和  int allsum = 0;  int cardNoLength = (int)[cardNo length];  int lastNum = [[cardNo substringFromIndex:cardNoLength-1] intValue];    cardNo = [cardNo substringToIndex:cardNoLength - 1];  for (int i = cardNoLength -1 ; i>=1;i--) {    NSString *tmpString = [cardNo substringWithRange:NSMakeRange(i-1, 1)];    int tmpVal = [tmpString intValue];    if (cardNoLength % 2 ==1 ) {      if((i % 2) == 0){        tmpVal *= 2;        if(tmpVal>=10)          tmpVal -= 9;        evensum += tmpVal;      }else{        oddsum += tmpVal;      }    }else{      if((i % 2) == 1){        tmpVal *= 2;        if(tmpVal>=10)          tmpVal -= 9;        evensum += tmpVal;      }else{        oddsum += tmpVal;      }    }  }    allsum = oddsum + evensum;  allsum += lastNum;  if((allsum % 10) == 0)    return YES;  else    return NO;}

/**  * 匹配Luhn算法：可用于检测银行卡卡号  * @param cardNo  * @return  */ public static boolean matchLuhn(String cardNo) {   int[] cardNoArr = new int[cardNo.length()];   for (int i=0; i<cardNo.length(); i++) {     cardNoArr[i] = Integer.valueOf(String.valueOf(cardNo.charAt(i)));   }   for(int i=cardNoArr.length-2;i>=0;i-=2) {     cardNoArr[i] <<= 1;     cardNoArr[i] = cardNoArr[i]/10 + cardNoArr[i]%10;   }   int sum = 0;   for(int i=0;i<cardNoArr.length;i++) {     sum += cardNoArr[i];   }   return sum % 10 == 0; }

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{  NSString *text = [textField text];  NSCharacterSet *characterSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789/b"];  string = [string stringByReplacingOccurrencesOfString:@"-" withString:@""];  if ([string rangeOfCharacterFromSet:[characterSet invertedSet]].location != NSNotFound) {    return NO;  }    text = [text stringByReplacingCharactersInRange:range withString:string];  text = [text stringByReplacingOccurrencesOfString:@"-" withString:@""];    NSString *newString = @"";  while (text.length > 0) {    NSString *subString = [text substringToIndex:MIN(text.length, 4)];    newString = [newString stringByAppendingString:subString];    if (subString.length == 4) {      newString = [newString stringByAppendingString:@"-"];    }    text = [text substringFromIndex:MIN(text.length, 4)];  }    newString = [newString stringByTrimmingCharactersInSet:[characterSet invertedSet]];    if (newString.length >= 24) {    return NO;  }    [textField setText:newString];    return NO;}