Method with an array of inputs - objective-c

Question

I want to have a method where I can put as many arguments as I need like the NSArray:
- (id)initWithObjects:(id)firstObj, ... NS_REQUIRES_NIL_TERMINATION;
I can then use:
NSArray *array = [[NSArray alloc] initWithObjects:obj1, obj2, ob3, nil];
I can add as many objects as I want as long as I add 'nil' at the end to tell it I'm done.
My question is how would I know how many arguments were given, and how would I go through them one at a time?

Answer 1

- (void)yourMethod:(id) firstObject, ...
{
id eachObject;
va_list argumentList;
if (firstObject)
{
// do something with firstObject. Remember, it is not part of the variable argument list
[self addObject: firstObject];
va_start(argumentList, firstObject); // scan for arguments after firstObject.
while (eachObject = va_arg(argumentList, id)) // get rest of the objects until nil is found
{
// do something with each object
}
va_end(argumentList);
}
}

Answer 2

I think what you're talking about is implementing a variadic method. This should help: Variable arguments in Objective-C methods

Answer 3

I haven't had experience with these variadic methods (as they're called), but there's some Cocoa functionality to deal with it.
From Apple's Technical Q&A QA1405 (code snippet):
- (void)appendObjects:(id)firstObject, ...
{
id eachObject;
va_list argumentList;
if (firstObject) // The first argument isn't part of the varargs list,
{ // so we'll handle it separately.
[self addObject:firstObject];
va_start(argumentList, firstObject); // Start scanning for arguments after firstObject.
while ((eachObject = va_arg(argumentList, id))) // As many times as we can get an argument of type "id"
{
[self addObject:eachObject]; // that isn't nil, add it to self's contents.
}
va_end(argumentList);
}
}
Copied from http://developer.apple.com/library/mac/#qa/qa2005/qa1405.html

Answer 4

I would try this: http://www.numbergrinder.com/node/35
Apple provides access in their libraries for convenience. The way to know how many elements you have is by iterating over the list until you hit nil.
What I would recommend, however, if you want to pass a variable number of arguments into some method you're writing, just pass an NSArray and iterate over that array.
Hope this helps!