Saving a Reference to an Entity (Save/Load Persistence)

[Draco18s 2414]

I need to be able to save out and then reload a reference to a Minecart, because the TileEntity is "catching" it and hold it in place until its finished, then reapplying some momentum to it when its done, so that the cart continues on its merry way.

 

Problem is, I can't seem to make that "reapplying some momentum to it when its done" part work after a save/load because I literally have no way of getting an entity from the World by anything other than incremental spawn ID (not guaranteed to persist, AFAIK) or by AABB (not save-able or not able to ensure match).

 

What am I missing?

[diesieben07 7696]

Use UUIDs and search in a confined space, so you don't have to check every entity in the world. That's how leashes work, too.

[TheGreyGhost 819]

Hi

 

I think you could try three things - One is to "leash" your minecart similar to what DieSieben suggested, not sure if that works for non-EntityLiving.  Second is to replace the vanilla Minecart Entity with a MyCapturableMinecart extends EntityMinecart to make it responsible for maintaining a link to the "capturing" tileentity, or thirdly your TileEntity could despawn the Minecart while it is captured and respawn once it's finished.

 

-TGG

 

> I literally have no way of getting an entity from the World by anything other than incremental spawn ID

PS forgot to mention- do you already know about persistent EntityID ?

i.e. getPersistentID() or getUniqueID() instead of getEntityId()

[Draco18s 2414]

> I literally have no way of getting an entity from the World by anything other than incremental spawn ID

PS forgot to mention- do you already know about persistent EntityID ?

i.e. getPersistentID() or getUniqueID() instead of getEntityId()

 

Oh, I can get a persistent ID all I want.

 

I have no way of going "Hey, server, find me this non-living entity by this UUID."  I can get players by UUID, but not any thing else.

 

Use UUIDs and search in a confined space, so you don't have to check every entity in the world. That's how leashes work, too.

 

I'll take a look at leashes.  I was going that route, but I wasn't sure if that'd even work for entities like minecarts (its not transparent on if those are saved/loaded and keep the same UUID, or what.  I would assume so, but you know what they say about about assuming...).

[coolAlias 746]

Also keep in mind that your entity reference will always return null if the chunk that it is in is not currently loaded. I've gotten around that by also storing the last known chunk coordinates, then force loading those chunks for the search when necessary.

 

As diesieben pointed out, though, it might not be a bad idea to store the coordinates anyway for the sake of narrowing your search. For my part, I just use the UUID when the entityId is no longer valid, and use the entityId once the entity is found.

 

See here.

[Draco18s 2414]

Also keep in mind that your entity reference will always return null if the chunk that it is in is not currently loaded. I've gotten around that by also storing the last known chunk coordinates, then force loading those chunks for the search when necessary.

 

TE and cart will be in the same chunk.  Specifically 1 block away from each other.

[coolAlias 746]

Also keep in mind that your entity reference will always return null if the chunk that it is in is not currently loaded. I've gotten around that by also storing the last known chunk coordinates, then force loading those chunks for the search when necessary.

 

TE and cart will be in the same chunk.  Specifically 1 block away from each other.

In that case you can simply store the UUID, and if the world#getEntityById returns null, get a list of entities in a bounding box enclosing that area and iterate through them until you find one with a matching UUID - there's your minecart.

[Draco18s 2414]

Yep, just got it working.

Did a slightly larger volume, just in case the cart gets away for any reason.

 

Thanks muchly.