Artemis Entity System Framework

Question

I am new to Artemis Entity Systems framework, and I want to know whether there is a way to get all the entities that have a specific component or components in them? (There should be, but I cannot find.)

For example I want to find all entities that have a EnemyComponent and check if they collide with any of the entities that have BulletComponent in them. How can I do this?

Answer 1

What you can do is to create a system which will be called in your collision system to get the list of all entities with chosen components.

For example:

public class FindBulletsSystem extends EntitySystem {
  private ImmutableBag<Entity> bullets;
  private boolean processingFlag = false;

  public FindBulletsSystem () {
    super(Aspect.getAspectForAll(BulletComponent.class));

  }

  @Override
  protected boolean checkProcessing() {
    if (processingFlag) {
      processingFlag = false;
      return true;
    }
    return false;
  }

  @Override
  protected void processEntities(ImmutableBag<Entity> entities) {
         bullets = entities;

  }

  public ImmutableBag<Entity> getAllBullets() {
    bullets = null;
    processingFlag = true;

    this.process();
    return bullets;
  }

}

In your collision system you can get bullets by calling this system:

world.getSystem(FindBulletsSystem.class).getAllBullets();