Configuration

Configurations define settings and consumer preferences that can be applied to a mod instance. Forge uses a configuration system using TOML files and read with NightConfig.

Creating a Configuration

A configuration can be created using a subtype of IConfigSpec. Forge implements the type via ForgeConfigSpec and enables its construction through ForgeConfigSpec$Builder. The builder can separate the config values into sections via Builder#push to create a section and Builder#pop to leave a section. Afterwards, the configuration can be built using one of two methods:

Method	Description
build	Creates the ForgeConfigSpec.
configure	Creates a pair of the class holding the config values and the ForgeConfigSpec.

note

ForgeConfigSpec$Builder#configure is typically used with a static block and a class that takes in ForgeConfigSpec$Builder as part of its constructor to attach and hold the values:

// In some config class
ExampleConfig(ForgeConfigSpec.Builder builder) {
  // Define values here in final fields
}

// Somewhere the constructor is accessible
static {
  Pair<ExampleConfig, ForgeConfigSpec> pair = new ForgeConfigSpec.Builder()
    .configure(ExampleConfig::new);
  // Store pair values in some constant field
}

Each config value can be supplied with additional context to provide additional behavior. Contexts must be defined before the config value is fully built:

Method	Description
comment	Provides a description of what the config value does. Can provide multiple strings for a multiline comment.
translation	Provides a translation key for the name of the config value.
worldRestart	The world must be restarted before the config value can be changed.

ConfigValue

Config values can be built with the provided contexts (if defined) using any of the #define methods.

All config value methods take in at least two components:

• A path representing the name of the variable: a . separated string representing the sections the config value is in
• The default value when no valid configuration is present

The ConfigValue specific methods take in two additional components:

• A validator to make sure the deserialized object is valid
• A class representing the data type of the config value

// For some ForgeConfigSpec$Builder builder
ConfigValue<T> value = builder.comment("Comment")
  .define("config_value_name", defaultValue);

The values themselves can be obtained using ConfigValue#get. The values are additionally cached to prevent multiple readings from files.

Additional Config Value Types

• Range Values
  • Description: Value must be between the defined bounds
  • Class Type: Comparable<T>
  • Method Name: #defineInRange
  • Additional Components:
    • The minimum and maximum the config value may be
    • A class representing the data type of the config value

note

DoubleValues, IntValues, and LongValues are range values which specify the class as Double, Integer, and Long respectively.

• Whitelisted Values

  • Description: Value must be in supplied collection
  • Class Type: T
  • Method Name: #defineInList
  • Additional Components:
    • A collection of the allowed values the configuration can be

• List Values

  • Description: Value is a list of entries
  • Class Type: List<T>
  • Method Name: #defineList, #defineListAllowEmpty if list can be empty
  • Additional Components:
    • A validator to make sure a deserialized element from the list is valid

• Enum Values

  • Description: An enum value in the supplied collection
  • Class Type: Enum<T>
  • Method Name: #defineEnum
  • Additional Components:
    • A getter to convert a string or integer into an enum
    • A collection of the allowed values the configuration can be

• Boolean Values

  • Description: A boolean value
  • Class Type: Boolean
  • Method Name: #define

Registering a Configuration

Once a ForgeConfigSpec has been built, it must be registered to allow Forge to load, track, and sync the configuration settings as required. Configurations should be registered in the mod constructor via ModLoadingContext#registerConfig. A configuration can be registered with a given type representing the side the config belongs to, the ForgeConfigSpec, and optionally a specific file name for the configuration.

// In the mod constructor with a ForgeConfigSpec CONFIG
ModLoadingContext.get().registerConfig(Type.COMMON, CONFIG);

Here is a list of the available configuration types:

Type	Loaded	Synced to Client	Client Location	Server Location	Default File Suffix
CLIENT	Client Side Only	No	.minecraft/config	N/A	-client
COMMON	On Both Sides	No	.minecraft/config	<server_folder>/config	-common
SERVER	Server Side Only	Yes	.minecraft/saves/<level_name>/serverconfig	<server_folder>/world/serverconfig	-server

tip

Forge documents the config types within their codebase.

Configuration Events

Operations that occur whenever a config is loaded or reloaded can be done using the ModConfigEvent$Loading and ModConfigEvent$Reloading events. The events must be registered to the mod event bus.

caution

These events are called for all configurations for the mod; the ModConfig object provided should be used to denote which configuration is being loaded or reloaded.