Is the 1st argument of an Objective C variadic function mandatory?

Question

Here is an example of a variadic function in Obj C.

// This method takes an object and a variable number of args
- (voi         


        

Answer 1

It doesn't have to be anything really. There are two hidden arguments to every Objective-C method, self, and _cmd (in that order). self is self-explanatory (haha), but a lesser-known one is _cmd, which is simply the selector that was used to invoke the current method. This makes it possible to use variadic arguments with Objective-C methods seemingly without using an initial argument like you do with a standard variadic C function.

- (void) someMethod:...
{
    va_list va;

    va_start(va, _cmd);

    // process all args with va_arg

    va_end(va);
}

Then you can call the method like this:

 [someObj someMethod:1, 2, 3];