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EntityLinkManager Listeners
Adrian Papari edited this page Jan 7, 2019
·
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You can react to established and killed links, and changed or dead referenced entities using per-field listeners.
LinkListener, or for convenience - LinkAdapter, bind to the field of a component type.
public class Child extends Component {
public Entity parent; // linked field
}
LinkListener<Child> |
trigger |
---|---|
::onLinkEstablished(owner, target) |
child.parent updated after being null
|
::onTargetChanged(owner, newTarget, oldTarget) |
child.parent points to new entity |
::onTargetDead(owner, deadTarget) |
referenced entity deleted (field auto-reset to null or -1) |
::onLinkKilled(owner, target) |
component removal - possibly due to entity deletion |
Consider a component:
/** anchors this entity to {@code target} entity */
public class Anchor extends Component {
@EntityId int target = -1;
}
If target
entity is deleted, we want to remove the Anchor
component,
as it no longer points to an active entity.
To remove component with dangling reference:
world.getSystem(EntityLinkManager.class).register(Anchor.class,
new LinkAdapter() {
// relevant fields are injected by default
private ComponentMapper<Anchor> mAnchor;
@Override
public void onTargetDead(int sourceId, int deadTargetId) {
// deadTargetId is the deleted entity currently referenced
// by Anchor, owned by entity with sourceId
mAnchor.remove(sourceId);
}
});
world.delete(targetId);
world.process(); // fires onTargetDead
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