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;

}