public class AddItemModifier extends LootModifier {

    private final Item item;

    private final CompoundTag compoundTag;

    public static final Supplier<Codec<AddItemModifier>> CODEC =
            Suppliers.memoize(() -> RecordCodecBuilder.create(inst -> codecStart(inst)
                    .and(ForgeRegistries.ITEMS.getCodec().fieldOf("item").forGetter(m -> m.item))
                   //I didn't find anything about CompoundTag in ForgeRegistries?  ForgeRegistries.BIOMES be replaced with?                 
                    .and(ForgeRegistries.BIOMES.getCodec().fieldOf("nbt").forGetter(m -> m.compoundTag))
                    .apply(inst, AddItemModifier::new)));

    protected AddItemModifier(LootItemCondition[] conditionsIn, Item item, CompoundTag compoundTag) {
        super(conditionsIn);
        this.item = item;
        this.compoundTag = compoundTag;
    }

    @Override
    protected @NotNull ObjectArrayList<ItemStack> doApply(ObjectArrayList<ItemStack> generatedLoot,
                                                          LootContext context) {
        if (context.getRandom().nextFloat() >= 0.4f) {
            ItemStack out = new ItemStack(item);
            if (compoundTag != null) {
                out.setTag(compoundTag);
            }
            generatedLoot.add(new ItemStack(item));
        }
        return generatedLoot;
    }

    @Override
    public Codec<? extends IGlobalLootModifier> codec() {
        return CODEC.get();
    }
}

 

loot_modifiers folder

{
  "type": "chinacraft:add_item",
  "conditions": [
    {
      "condition": "forge:loot_table_id",
      "loot_table_id": "minecraft:chests/nether_bridge"
    }
  ],
  "item": "patchouli:guide_book",
  "nbt": "{\"patchouli:book\":\"chinacraft:mencius\"}"
}

thank you ！ 

hmm...

4 hours ago, Spring said:

            ItemStack out = new ItemStack(item);
            if (compoundTag != null) {
                out.setTag(compoundTag);
            }
            generatedLoot.add(new ItemStack(item));

so make a stack, okay, set the tag, okay (i'll just assume you tried that), then disregard the stack you made, make a new one without tag and put in into drops...

might work...

 

On 12/13/2022 at 4:16 PM, MFMods said:

hmm...

so make a stack, okay, set the tag, okay (i'll just assume you tried that), then disregard the stack you made, make a new one without tag and put in into drops...

might work...

 

 

On 12/13/2022 at 11:50 AM, Spring said:

.and(ForgeRegistries.BIOMES.getCodec().fieldOf("nbt").forGetter(m -> m.compoundTag))

Maybe I didn't express my problem well.

But now it has been solved. This line of code is compiled incorrectly.

 

But I did。

public class AddItemTagModifier extends LootModifier {

    public static final Codec<CompoundTag> TAG_CODEC = Codec.PASSTHROUGH.comapFlatMap((convert) -> {
        Tag tag = convert.convert(NbtOps.INSTANCE).getValue();
        String replace = tag.toString().replace("'", "");
        CompoundTag compoundtag = null;
        try {
            compoundtag = TagParser.parseTag(replace);
        } catch (CommandSyntaxException e) {
            e.printStackTrace();
        }
        return DataResult.success(compoundtag);
    }, (value) -> new Dynamic<>(NbtOps.INSTANCE, value));

    private final Item item;

    private final CompoundTag compoundTag;

    public static final Supplier<Codec<AddItemTagModifier>> CODEC =
            Suppliers.memoize(() -> RecordCodecBuilder.create(inst -> codecStart(inst)
                    .and(ForgeRegistries.ITEMS.getCodec().fieldOf("item").forGetter(m -> m.item))
                    .and(TAG_CODEC.fieldOf("nbt").forGetter(m -> m.compoundTag))
                    .apply(inst, AddItemTagModifier::new)));

    protected AddItemTagModifier(LootItemCondition[] conditionsIn, Item item, CompoundTag compoundTag) {
        super(conditionsIn);
        this.item = item;
        this.compoundTag = compoundTag;
    }

    @Override
    protected @NotNull ObjectArrayList<ItemStack> doApply(ObjectArrayList<ItemStack> generatedLoot,
                                                          LootContext context) {
        if (context.getRandom().nextFloat() >= 0.4f) {
            ItemStack out = new ItemStack(item);
            if (compoundTag != null) {
                out.setTag(compoundTag);
            }
            generatedLoot.add(out);
        }
        return generatedLoot;
    }

    @Override
    public Codec<? extends IGlobalLootModifier> codec() {
        return CODEC.get();
    }

It works very well ！