[Solved] Can I keep Capability data when breaking and replacing a vanilla Block?

[longbowrocks]

I've written a mod that adds a Capability with persistent state to chest type TileEntities (TileEntityChest, TileEntityShulkerBox). I would like to pick up a chest and put it back down without losing my Capability state, but from what I've read in both code and forums, that doesn't seem possible without editing breakBlock() for the affected classes, or replacing the classes with my own (either way, that sounds like a core mod).

 

If I want to do this, does it have to be a core mod, or have I missed something?

Edited March 4, 2018 by longbowrocks
solved

[Daeruin]

I did something like this with a container that keeps its contents when broken, but my memory is of it is a little fuzzy. I think you can write NBT data to the dropped ItemStack, but you have to override Block#removedByPlayer to return true if willHarvest is true, in order to prevent the tile entity from being deleted too early in the process. Then override harvestBlock, I think, to write the NBT data into an ItemStack and spawn it as an EntityItem.

[longbowrocks]

That sounds about right, but in this case that would be a core mod (I think so anyway. There appear to be multiple definitions for core mod spread across the net, so I can only assume "core mod" means "anything that modifies the vanilla Minecraft code instead of extending/adding to it")

[Draco18s]

1 hour ago, longbowrocks said:

That sounds about right, but in this case that would be a core mod (I think so anyway. There appear to be multiple definitions for core mod spread across the net, so I can only assume "core mod" means "anything that modifies the vanilla Minecraft code instead of extending/adding to it")

A core mod is one that uses ASM to make changes to code that you do not control through the class loading process.

You will find very little help writing such code, as it is very easy to do things Badly and cause more problems than you solve.

[Daeruin]

I somehow missed that you were adding this capability to vanilla blocks. You might consider creating a custom item that drops instead of the vanilla item when a vanilla block with your Capability is broken. You could write the NBT data to the custom item during the HarvestDropsEvent and remove the vanilla drop. If you wanted, you could even give the custom item the same texture and unlocalized name to make it appear like the vanilla version. Then have the custom item place the vanilla block when right clicked.

Edited March 3, 2018 by Daeruin

[longbowrocks]

3 hours ago, diesieben07 said:

This might be possible using the following hack:

• In BlockEvent.BreakEvent you need to grab the data from the tile entity (if a relevant tile entity is being broken) and store it in a ThreadLocal<YOUR_DATA>. This makes sure to isolate server and client thread in single player.
• Then in BlockEvent.HarvestDropsEvent you can access the thread local and have access to the data (which you would otherwise not have since the tile entity is gone at this point). You can now store the data in the created drop stack.

Damn. Between brainstorming and reading vanilla code , I forgot that I hadn't finished looking through the events provided by forge!

 

Thank you diesieben07, I'll have to try that when I get home today. I managed to confirm that I can write the NBT to an ItemStack before I left, and I should be able to read the NBT with BlockEvent.PlaceEvent.

[longbowrocks]

Yep, that works.