title: Processing varargs before passing them on
body: <p>I'd like to build a function that has the same signature as <code>NSString</code>'s <code>stringWithFormat:</code> (with the varargs), but I'd like to URL encode each argument before I pass it along to <code>stringWithFormat:</code> itself. I already have a method <code>+ (NSString *)urlEncode:(NSString *)s</code> that does the encoding. How do I build the va_list with the encoded arguments?</p>