[1.12.2] Creating New World-Bound Items After Initilization

[JavaIsBetterThanJavaScript]

While I know Java pretty well, I am very new to modding. In my mod I want to add metallurgy. The fundamentals of the mod is creating new alloys through the use of a special crafting table. Each alloy has five attributes: strength, durability, resistance, density and weight. These could easily be set to int fields. But the problem I am running into is how I can create new items after everything has been initiliazed. Can I even do this? Would I just have to modify attributes of a base Alloy item? If it is possible, I would like to add it to the world's save. Is it possible to create a new folder alloys in each save, put JSON files into it and save the alloy's attributes within the JSON? This would have the benefit of the user being able to drag-and-drop their alloys into new worlds. It would also be nice to give the user the the ability to do: //give @s [modid]:[alloy_name], or at least //give @s [modid]:alloy 1 0 {type:[alloy_name]}. Anyways, thanks!

[Matryoshika]

You can not create any item after pre-initialization has finished. The code is built specifically to that effect.

 

If you must, you can allow the end-user to create new items through JSON or any other means, but those items will not exist until Minecraft launches once more, and detects the new items during the registry-events.
This however has it's drawbacks, especially with constant addition and possibly subtractions from the registries.

It would be for the best if you created a base-alloy item, register that once, and then edit it's stat with NBT, similarily to how Tinkers' Construct creates it's tools.
You can edit many, many different client-side stats of the alloys, such as name, icon/model etc, to distinguish them. They will still all use the same [modid]:[name] but again, as with Tinker tools, you can spawn them in with specific NBT data.
If you sort out all your different possible stats (or just some of them) the different alloys can be added to your CreativeTab (and thus also automatically into JEI if installed) to make it simpler to spawn in.

Edited March 20, 2019 by Matryoshika

[JavaIsBetterThanJavaScript]

Not very surprised that items cannot be created post-initalization. So how would I go about adding the same item just with different attibutes into the creative menu? Would I create a static method in a AlloyHandler class that retrieves all the valid alloys present in the save's files?

[JavaIsBetterThanJavaScript]

When saving the alloy's attributes to the world's save folder, is there anything different/special than regular Java file 'management'?

[JavaIsBetterThanJavaScript]

Things like its name, strength, weight etc.

[Cadiboo]

7 hours ago, Matryoshika said:

You can not create any item after pre-initialization has finished. The code is built specifically to that effect.

Not quite correct. Registries events (where you should be making your items) are fired right after preInit. But yes, after these events finish firing, you can’t add any objects to any registries. 

[Draco18s]

I do something like this in one of my mods:

https://github.com/Draco18s/ReasonableRealism/blob/1.12.1/src/main/java/com/draco18s/industry/item/ItemCastingMold.java

 

It has a model defined by its nbt values. I even create a new variant over here in a different mod:

https://github.com/Draco18s/ReasonableRealism/blob/1.12.1/src/main/java/com/draco18s/farming/integration/IndustryIntegration.java

 

Note also that this method can't create new models after the registry events either, though in this case it is because of the way the model bakery works, but there are solutions for more dynamic models (but I didn't need it). You could easily use a colored model for something like metal ingots, which would all use a single predefined model but with a color multiplier that can be whatever value you want. 

 

For things like attack damage and durabilit, you're going to want to take a look at this (older 1.10 code that hasn't been updated):

https://github.com/Draco18s/Artifacts/blob/master/main/java/com/draco18s/artifacts/item/ItemArtifact.java