Question

I’ve been searching all through the web and I seem to not find any alternate way of doing comparing if two polymorphic objects are the same type, or if a polymorphic object IS a type. The reason for this is because I am going to implement a Entity System inside of my game that I am currently creating.

I have not found another way of doing this other than with the use macros or a cast (the cast not being a portable method of doing so). Currently this is how I am identifying objects, is there a more efficient or effective way of doing this? (without the use of C++ RTTI)

I pasted it on pastebin, since pasting it here is just too much of a hassle.
http://pastebin.com/2uwrb4y2

And just incase you still do not understand exactly what I’m trying to achieve, I’ll try to explain it. An entity in a game is like an object inside of the game (e.g. a player or enemy), it have have components attached to it, these components are data for an entity. A system in the entity system is what brings the data and logic of the game together.

For example, if I wanted to display a model up on the screen it would be similar to this:

World world; // Where all entities are contained

// create an entity from the world, and add
// some geometry that is loaded from a file
Entity* e = world.createEntity();
e->add(new GeometryComponent());
e->get<GeometryComponent>()->loadModel("my_model.obj"); // this is what I want to be able to do


world.addSystem(new RenderingSystem());

// game loop
bool isRunning = true;
while(isRunning) 
{
   pollInput();
   // etc...      

   // update the world
   world.update();
}

EDIT:
Here’s a framework, programmed in Java, that does mainly what I want to be able to do.
http://gamadu.com/artemis/tutorial.html

Answer 1

See std::is_polymorphic. I believe boost has it too.

If T is a polymorphic class (that is, a class that declares or inherits at least one virtual function), provides the member constant value equal true. For any other type, value is false.

http://en.cppreference.com/w/cpp/types/is_polymorphic

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Edit:

Why can’t you just do this in your example?

Entity* e = world.createEntity();
GemoetryComponent* gc = new GeometryComponent();
gc->loadModel("my_model.obj");
e->add(gc);

Create the structure before stripping the type information.