Custom Conditions

Mods can add custom conditions that can be used to lock entries or categories. To this end you need to:

1. Create a ResourceLocation ID for the new condition (e.g. mymod:my_condition)
2. Create a custom condition class with ID, CODEC, and STREAM_CODEC
3. Register the condition via a dedicated registry class
4. For datagen: create a condition model class
5. Finally use the condition in your book

tip

The ResourceLocation is what you will use in your entries and categories to gate them behind your custom condition.

Condition Class

Conditions need to extend BookCondition in the package com.klikli_dev.modonomicon.book.conditions.

Each condition class must declare three static fields:

• ID — a ResourceLocation (use Modonomicon.loc(...) or new ResourceLocation("mymod", "my_condition"))
• CODEC — a MapCodec<T> for JSON deserialization, typically built with RecordCodecBuilder.mapCodec(...)
• STREAM_CODEC — a StreamCodec<RegistryFriendlyByteBuf, T> for network serialization, typically built with StreamCodec.composite(...)

You must also override type() to return the corresponding BookConditionType<T> from your registry class.

See these example conditions for reference:

• BookModLoadedCondition
• BookFalseCondition
• BookResearchNodeUnlockedCondition

Condition Registration

Create a dedicated registry class to hold your condition registrations. Use public static final fields initialized via BookConditionTypeRegistry.register(...), and provide an empty bootstrap() method to trigger class loading:

public final class MyModModonomiconConditionRegistry {

    public static final BookConditionType<BookMyCustomCondition> MY_CUSTOM =
        BookConditionTypeRegistry.register(
            BookMyCustomCondition.ID,
            BookMyCustomCondition.CODEC,
            BookMyCustomCondition.STREAM_CODEC
        );

    private MyModModonomiconConditionRegistry() {
    }

    public static void bootstrap() {
    }
}

Then call bootstrap() during FMLCommonSetupEvent (NeoForge) or your ModInitializer.onInitialize (Fabric):

// NeoForge
public void onCommonSetup(FMLCommonSetupEvent event) {
    MyModModonomiconConditionRegistry.bootstrap();
}

// Fabric
@Override
public void onInitialize() {
    MyModModonomiconConditionRegistry.bootstrap();
}

Condition Datagen Model

The model class helps you to generate the condition JSON files via DataGen.

Extend BookConditionModel<T> and override toBookCondition(HolderLookup.Provider) to return the runtime condition instance. Pass the condition's ID to the super(...) constructor.

See these example models for reference:

• BookModLoadedConditionModel
• BookFalseConditionModel
• BookResearchNodeUnlockedConditionModel

tip

You need not register the model.

Usage

On your entry or category, add:

{
  ...
  "condition": {
      "type": "mymod:my_condition"
  },
  ...
}

See also Unlock Conditions for more information on how to use conditions.