Easily create GET NSURLs in Objective-C. (Used in https://github.com/Gi-lo/GCXHTTPOperation )

gistfile1.m

- (NSURL *)URLWithString:(NSString *)string andQueryValuesForKeys:(NSString *)value, ... {
    if (!value) {
        return [NSURL URLWithString:string];
    }
    
    NSMutableString *queryString = [NSMutableString string];
    NSString *argument = nil;
    NSUInteger argumentCount = 0;

    va_list argumentList;
    va_start(argumentList, value);
   
    while ((argument = va_arg(argumentList, NSString *))) {
        argumentCount++;

        if (argumentCount % 2 == 0) {
            value = [argument serializedString];
        } else {
            NSString *separator = @"&";
            if (argumentCount == 1) {
                separator = @"?";
            }
            
            [queryString appendFormat:@"%@%@=%@", separator, argument, [value serializedString]];
        }
    }
    
    va_end(argumentList);

    NSAssert(argumentCount % 2 != 0, @"Uneven amount of query keys and values.");
    
    return [NSURL URLWithString:[string stringByAppendingString:queryString]];
}

Example usage:
NSURL *url = [self URLWithString:@"http://search.twitter.com/search.json" andQueryValuesForKeys:term, @"q", @"100", @"rpp", nil];