zallik zallik - 1 year ago 76
C++ Question

my c++ game architecture

I'm a fairly experienced programmer, but I'm still relatively new to OOP architecture and design in c++.
Most of my experience is with C# and Java. I recently endeavored to code up a simple game engine in c++.
I used SDL for the graphics. In this post, I would like to discuss my architecture and to get some feedback
on it. Particularly, I've run into a design issue that I would like some help with. So, here goes:

  • In my main function, I initialize all of the SDL stuff for drawing to the screen, etc.

  • Then I instantiate all of the objects that I intend to use: floor, wall, player, etc.

  • Next I start the main loop. This loop executes each object's movement, collision detection and collision handling functions, and redraws them.

  • The main loop runs until the application is quit, drawing one frame each iteration.

My problem is this:
I tried to do a kind of interface-style design. It involves a series of
abstract base classes that allow each object to implement a behavior. For example, if I want an object to be movable,
it would have to inherit from the movable base class which contains a virtual function called
and some position
coordinates. If I wanted it to be collidable, the object would inherit from the collidable abstract class, which
contains the virtual functions
as well as a hitbox member variable. An object
like the player inherits from both of these base classes as well as several others.

This works well enough as long as I'm doing everything by hand in the main loop. I can just say:


and it's fine. But I would like to
be able to have a vector or array of generic objects in the main loop and do something like this:

for each object in vector
if object is of type movable
if object is of type collidable

I thought that I could accomplish this with dynamic casting, but I really haven't been able to come up with anything.
I've tried storing them as void pointers, but that doesn't work the way I want it to. I've been reading about this
gameobject-component architecture for video games that I might try, but I'd really like to salvage what I've already
written. I figure this is a good learning opportunity. If anybody has any ideas I'd really appreciate it. How does my architecture compare to other simple game engine designs? does my interface architecture make sense or is it totally wonky?

Answer Source

If you work in C++, try SFML, it's faster than SDL, and if you know OpenGL, you can use it too.
For your problem:

class Entity {
     //constructor and other stuff
     void virtual exec() =0; ///<= pure virtual method

class Movable : Entity {
    void move(); //do somthing
    void exec() {move();};

class Collidable : Entity {
   void col(); //do your job
   void exec(){col();};

std::vector<Entity*> e_v;
///push some instance
for (Entity* e : e_v)
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