Objective-C protocols/interface?

I'm trying to write something similar to this (sorry if the sample is not 100% correct, im just writing off the top of me head):

interface Handler
{
   void doSomething ( );
}

otherclass
{
    void othermethod ( Handler handler )
    {
        // Handler do something
    }
}

So in ObjectiveC I made the following:

@protocol Handler
- (void) doSomething;
@end

// Other class
- (void) othermethod: (Handler*) handler
{
   // Do something
}

But I get the following error on the othermethod declaration line: Expected ')' before hander.

I know there is no syntax error here (I can replace Handler* with NSObject* and the error goes away), so obviously my use of a protocol in this case is incorrect.

Could anyone point me to the proper way of creating a C# like interface?

You want to use a type like this:

id <Handler> obj

This means "any object (type id) that implements the Handler protocol". The protocol goes in between the greater than/less than signs. You can also use a declaration like NSObject <Handler> *obj, which means "any object of type NSObject or a subclass that implements the Handler protocol".

You can also declare an object that implements several protocols like so:

id <Handler, OtherHandler> obj