判断用户输入的银行卡号是否正确--基于Luhn算法的格式校验

开发中，有时候，为了打造更好的用户体验，同时减轻服务器端的压力，需要对于一些如，手机号码，银行卡号，身份证号码进行格式校验

下面是判断银行卡号输入是否正确的代码（基于Luhn算法的格式校验）：

iOS代码：

/**

*  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;

}

Androd代码：

/**

* 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;

}

附（银行卡号格式化）：

在输入银行卡号过程中，通常，我们会每隔4位插入一个"-"，类似"1332-2131-2313-1231-212"这种的格式
可以通过以下方法实现：

设置textField的代理

- (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;

}

最后，怎么获得不包含符号"-"的银行卡号呢？

[self.textField.text stringByReplacingOccurrencesOfString:@"-" withString:@""]