Component Based Architecture in game development

I have been thinking of trying out component based architecture for game development. I have read some blog posts and articles about it but I have a few things I have not sorted out yet. When I say component based I mean that you can add components to a ComponentManager that updates all components in its list. I want to try this to avoid getting classes that inherits variables and functions that they don´t need. I really like the idea of having an really simple entity class with a lot of components working side by side without getting bloated. Also, it is easy to remove and add functionality at runtime wich makes it really cool.

This is what I am aiming for.

// this is what the setup could be like
entity.componentManager.add(new RigidBody(3.0, 12.0));
entity.componentManager.add(new CrazyMagneticForce(3.0));
entity.componentManager.add(new DrunkAffection(42.0, 3.0));

// the game loop updates the component manager which updates all components
entity.componentManager.update(deltaTime);

Communication: Some of the components need to communicate with other components

I can´t rely on the components to be self-sustaining. Sometime they will need to communicate with the other components. How do I solve this? In Unity 3D, you can access the components using GetComponent().

I was thinking of doing it like this, but what happens if you have two components of the same type? Maybe you get a Vector back.

var someComponent : RigidBody = _componentManager.getComponent(RigidBody);

Priority: Some components need to update before others

Some components need to update before others to get the correct data for the current game loop. I am thinking of adding a PRIORITY to each component, but I am not sure that this is enough. Unity uses LateUpdate and Update but maybe there is a way to get an even better control of the order of execution.

Well, thats it. If you have any thoughts don´t hesitate to leave a comment. Or, if you have any good articles or blogs about this I will gladly take a look at them. Thanks.

Component based game engine design

http://cowboyprogramming.com/2007/01/05/evolve-your-heirachy/

EDIT: My question is really how to solve the issue with p开发者_如何学运维riorities and communication between the components.

I settled for an RDMBS component entity system http://entity-systems.wikidot.com/rdbms-with-code-in-systems#objc

It is so far working really well. Each component only holds data and has no methods. Then I have subsystems that process the components and do the actual work. Sometimes a subsystem needs to talk to another and for that I use a service locator pattern http://gameprogrammingpatterns.com/service-locator.html

As for priorities. Each system is processed in my main game loop and so it is just a matter of which gets processed first. So for mine I process control, then physics, then camera and finally render.