Quick Formatting of Credit Card Numbers

#objective-c

#cocoa

#ios

#xcode

#regular expression

#nsstring

#credit cards

Ever wonder how you could format a credit card number in your app? Maybe you've tried a few different ways, for example: stringByReplacingOccurrencesOfString:withString:options:range

Well, let's save you some time with Regular Expressions :)

Please, step into my office—

 NSString *formattedCCNumber;
if ([self.creditCardNumber length] == 16) {
 formattedCCNumber = [self.creditCardNumber stringByReplacingOccurrencesOfString:@"(\\d{4})(\\d{4})(\\d{4})(\\d+)" withString:@"1ドル-2ドル-3ドル-4ドル" options:NSRegularExpressionSearch range:NSMakeRange(0, [self.creditCardNumber length])];
} else if ([self.creditCardNumber length] == 15) {
 formattedCCNumber = [self.creditCardNumber stringByReplacingOccurrencesOfString:@"(\\d{4})(\\d{6})(\\d+)" withString:@"1ドル-2ドル-3ドル" options:NSRegularExpressionSearch range:NSMakeRange(0, [self.creditCardNumber length])];
}

self.ccNumberTextField.text = formattedCCNumber;

And below is the method we replaced in stringByReplacingOccurrencesOfString:withString:options:range—

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:@""];

 // Change credit card display for AMEX.
 if ([text length] > 1 && [text characterAtIndex:0] == '3' && ([text characterAtIndex:1] == '4' || [text characterAtIndex:1] == '7')) {
 NSString *newString = @"";
 while (text.length > 0) {
 // First set of numbers.
 NSString *subString1 = [text substringToIndex:MIN(text.length, 4)];
 newString = [newString stringByAppendingString:subString1];
 if (subString1.length == 4) {
 newString = [newString stringByAppendingString:@"-"];
 }
 if (subString1.length < 5) {
 text = [text substringFromIndex:MIN(text.length, 4)];
 }
 // Second set of numbers.
 NSString *subString2 = [text substringToIndex:MIN(text.length, 6)];
 newString = [newString stringByAppendingString:subString2];
 if (subString2.length == 6) {
 newString = [newString stringByAppendingString:@"-"];
 }
 if (subString2.length < 7) {
 text = [text substringFromIndex:MIN(text.length, 6)];
 }
 // Third set of numbers.
 NSString *subString3 = [text substringToIndex:MIN(text.length, 5)];
 newString = [newString stringByAppendingString:subString3];
 if (subString3.length < 16) {
 text = [text substringFromIndex:MIN(text.length, 15)];
 }
 }
 newString = [newString stringByTrimmingCharactersInSet:[characterSet invertedSet]];
 if (newString.length > 17) {
 return NO;
 }
 [textField setText:newString];
 return NO;
 } else {
 // Display credit card number in sections of 4 for all other issuers.
 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 > 19) {
 return NO;
 }
 [textField setText:newString];
 return NO;
 }