Missing sentinel in method dispatch

Question

I want to create a subclass of NSMutableArray and need to override the -initWithObjects: method.

But How to call [super xxx];?

- (id) initWithObjects:(id)firstObj, ... {
    [super initWithObjects:firstObj]; // Error: Missing sentinel in method dispatch
    // Error: The result of a delegate init call must be immediately returned or assigned to "self"

}

Thanks.