Question

First let me explain what I don’t mean. I don’t want to type an argument to a protocol:

-(void)someMethod:(id<SomeProtocol>)someArgument;

What I do want to is to pass a protocol to a method in the same way I can pass a Class to a method (The following is incorrect, but it hopefully explains what I want to do):

-(void)someMethod:(Protocol)someArgument;

I would then like to be able to use the Protocol to check whether a set of objects implement it.

Answer 1

If you know the name of a protocol at coding-time, use @protocol(SomeProtocol) to get a pointer to that protocol, similar to how you’d use @selector(x).

Beyond that, you just refer to protocols with the class identifier Protocol — so you’re method declaration would look like:

-(void)someMethod:(Protocol*)someArgument

You can see an example in the docs for NSObject conformsToProtocol:

http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSObject_Class/Reference/Reference.html#//apple_ref/occ/clm/NSObject/conformsToProtocol: