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package com.artemis;
import com.artemis.annotations.DelayedComponentRemoval;
import com.artemis.utils.IntBag;
import com.artemis.utils.reflect.SystemMetadata;
import static com.artemis.utils.reflect.ReflectionUtil.implementsAnyObserver;
/**
* Tracks a subset of entities, but does not implement any sorting or iteration.
*
* @author Arni Arent
* @author Adrian Papari
*/
public abstract class BaseEntitySystem extends BaseSystem
implements EntitySubscription.SubscriptionListener {
private final Aspect.Builder aspectConfiguration;
protected EntitySubscription subscription;
public BaseEntitySystem() {
this(null);
}
/**
* Creates an entity system that uses the specified aspect as a matcher
* against entities.
*
* @param aspect to match against entities
*/
public BaseEntitySystem(Aspect.Builder aspect) {
if (aspect == null) {
aspect = new SystemMetadata(getClass()).getAspect();
if (aspect == null) {
String error = "Aspect was null and no aspect annotations set on system (@All); to use systems which " +
"do not subscribe to entities, extend BaseSystem directly.";
throw new NullPointerException(error);
}
}
aspectConfiguration = aspect;
}
protected void setWorld(World world) {
super.setWorld(world);
subscription = getSubscription();
if (implementsAnyObserver(this))
subscription.addSubscriptionListener(this);
}
/**
* @return entity subscription backing this system.
*/
public EntitySubscription getSubscription() {
final AspectSubscriptionManager sm = world.getAspectSubscriptionManager();
return sm.get(aspectConfiguration);
}
@Override
public void inserted(IntBag entities) {
int[] ids = entities.getData();
for (int i = 0, s = entities.size(); s > i; i++) {
inserted(ids[i]);
}
}
/**
* Gets the entities processed by this system. Do not delete entities from
* this bag - it is the live thing.
*
* @return System's entity ids, as matched by aspect.
*/
public IntBag getEntityIds() {
return subscription.getEntities();
}
/**
* Called if entity has come into scope for this system, e.g created or a component was added to it.
*
* Triggers right after any system finishes processing. Adding and immediately removing a component
* does not count as a permanently change and will prevent this method from being called.
*
* Not triggered for entities that have been destroyed immediately after being created (within a system).
*
* @param entityId the entity that was added to this system
*/
protected void inserted(int entityId) {
}
/**
* Called if entity has gone out of scope of this system, e.g deleted
* or had one of it's components removed.
*
*
Explicitly removed components are only retrievable at this point
* if annotated with {@link DelayedComponentRemoval}.
*
*
Deleted entities retain all their components - until all listeners
* have been informed.
*
* @param entities entities removed from this system.
*/
@Override
public void removed(IntBag entities) {
int[] ids = entities.getData();
for (int i = 0, s = entities.size(); s > i; i++) {
removed(ids[i]);
}
}
/**
* Called if entity has gone out of scope of this system, e.g deleted
* or had one of it's components removed.
*
* Important note on accessing components:
* Using {@link ComponentMapper#get(int)} to retrieve a component is unsafe, unless:
* - You annotate the component with {@link DelayedComponentRemoval}.
* - {@link World#isAlwaysDelayComponentRemoval} is enabled to make accessing all components safe,
* for a small performance hit.
*
* {@link ComponentMapper#has(int)} always returns {@code false}, even for DelayedComponentRemoval components.
*
* Can trigger for entities that have been destroyed immediately after being created (within a system).
*
* @param entityId the entity that was removed from this system
*/
protected void removed(int entityId) {
}
}