gistfile1.m

@implementation NSString (ContactExtension)

- (NSString*)stringFormattedAsPhoneNumber {
	NSMutableString *newString = nil;
	BOOL prependPlus = NO;
	
	if (!self)
		return nil;
	
	if ([self characterAtIndex:0] == '+')
		prependPlus = YES;
	
	unsigned len = self.length;
	NSCharacterSet *numericSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789"];
	newString = [NSMutableString string];
	NSRange range = NSMakeRange(0, 0), tempRange;
	
	while (NSMaxRange(range) <= len) {
		tempRange = [self rangeOfCharacterFromSet:numericSet options:NSLiteralSearch range:NSMakeRange(NSMaxRange(range), len - NSMaxRange(range))];
		if (NSMaxRange(range) == tempRange.location) {
			range.length += tempRange.length;
		} else {
			[newString appendString:[self substringWithRange:range]];
			range = tempRange;
		}
	}
	
	char tmpChar;
	unsigned int offset = 0;
	switch (newString.length) {
		case 11:
			tmpChar = [newString characterAtIndex:0+offset];
			if (tmpChar != '1') { [newString setString:self]; prependPlus = NO; break; }
			
			[newString insertString:@" " atIndex:1];
			offset += 2;
		case 10:
			tmpChar = [newString characterAtIndex:0+offset];
			if (tmpChar == '0' || tmpChar == '1') { [newString setString:self]; prependPlus = NO; break; }
			
			[newString insertString:@"(" atIndex:0+offset];
			[newString insertString:@") " atIndex:4+offset];
			offset += 6;
		case 7:
			tmpChar = [newString characterAtIndex:0+offset];
			if (tmpChar == '0' || tmpChar == '1') { [newString setString:self]; prependPlus = NO; break; }
			
			[newString insertString:@"-" atIndex:3+offset];
			break;
		default:
			// Non-standard number format - use the original string
			[newString setString:self];
			prependPlus = NO;
			break;
	}
	
	if (prependPlus)
		[newString insertString:@"+" atIndex:0];
		
	return newString;
}

@end