验证银行卡号是否正确

话不多说，直接上代码，不懂可留言：

 

- (void)viewDidLoad {
    [super viewDidLoad];
   
   

}

- (BOOL) checkCardNo:(NSString*) cardNo{
    int oddsum = 0;   
    int evensum = 0;  
    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;
}

- (IBAction)Btn:(id)sender {
   
    NSString *str = self.NumTF.text;
    BOOL isRight = [self checkCardNo:str];
    if (!isRight) {
       
        UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"不对" message:@"请重新输入卡号" delegate:nil cancelButtonTitle:@"取消" otherButtonTitles:nil, nil ,nil];
        [alert show];
    }else{
        UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"对" message:@"" delegate:nil cancelButtonTitle:@"取消" otherButtonTitles:nil, nil ,nil];        [alert show];}   

}