Weak Reference

[jeffryfisher]

A year ago, in another thread, D7 posted this not quite compilation-ready suggestion:

 

Basically instead of having a field of type EntityPlayer in your class you have a WeakReference<EntityPlayer> and a UUID like this:

private final WeakReference<EntityPlayer> ownerEntity = new WeakReference<EntityPlayer>();
private UUID ownerID;

public void setOwner(EntityPlayer owner) {
    this.ownerID = owner.getUniqueID();
    this.ownerEntity.set(owner);
}

public EntityPlayer getOwnerEntity() {
    EntityPlayer owner = ownerEntity.get();
    if (owner == null || owner.isDead) {
        owner = lookupOwner();
    }
    return owner;
}

public UUID getOwnerID() {
    return ownerID;
}

private EntityPlayer lookupOwner() {
    if (ownerID == null) {
        return null;
    }
    List<EntityPlayerMP> allPlayers = MinecraftServer.getServer().getConfigurationManager().playerEntityList;
    for (EntityPlayerMP player : allPlayers) {
        if (player.getUniqueID().equals(ownerID)) {
            ownerEntity.set(player);
            return player;
        }
    }
    return player;
}

And then whenever you need the player, use getOwnerEntity. It will return null if the player is not online. And save the UUID to NBT of course.

 

This smacks of a reusable interface (e.g. "IWeakOwnerID"). Does such an interface exist in Forge that my class could implement? Or am I imagining things; should I copy-paste and tailor the example to suit the mod I am about to make?

 

If the answer is "not yet", then I'll make the attempt to first generalize an interface and then implement it. In that case, would anyone be interested in seeing the interface's code if I succeed?

[Draco18s]

https://docs.oracle.com/javase/7/docs/api/java/lang/ref/WeakReference.html

 

It's a generic.

[jeffryfisher]

Weak Reference itself is a generic, but the example of code using it looks like an opportunity to code something reusable.

 

I learned something about interfaces. I've coded classes implementing them, but I've never designed one. I am now bummed that I can't put instance methods into one. This leaves me wishing that Java would allow multiple inheritance.

 

Alas, the code to manage a weak reference to a player/owner must either be replicated where used or else embodied in a class. I'm going to set it aside until my mod (a pressure plate that only triggers when stepped on by the player who placed it) is ready. Then I'll have a better idea how and where it might fit. Maybe then I'll try to design something that can be reused.

[BusyBeever]

You dont really need multiple inheritance if you are designing your code correct.

[Choonster]

Managing an owner like this could be a potential use-case for the new Capability system.