Creating a Condition

A condition is a check that must be true before an effect can run or stay on. This page tells you how to make one. For the terms on this page, see the Glossary.

Make a condition

Make a Kotlin object that extends Condition<T>. Give the ID to the constructor.
Set T to NoCompileData if you do not need compile data.
Add the arguments that the user must write.
Override isMet. Return true if the condition is true for the dispatcher.

object ConditionWearingElytra : Condition<NoCompileData>("wearing_elytra") {
    override val description = "Passes when the player wears an elytra."

    // The result changes only when the items of the player change.
    override val invalidatedBy = setOf(HolderChange.Items)

    override fun isMet(
        dispatcher: Dispatcher<*>,
        config: Config,
        holder: ProvidedHolder,
        compileData: NoCompileData
    ): Boolean {
        val player = dispatcher.get<Player>() ?: return false
        return player.inventory.chestplate?.type == Material.ELYTRA
    }
}

When libreforge checks a condition

Libreforge checks the conditions of permanent effects again and again. The invalidatedBy property tells libreforge when to do this.

`invalidatedBy` value	Libreforge checks the condition
`null` (default)	At a fixed interval. Use this if you do not know which events change the result.
A set of `HolderChange` values	Only after one of these changes occurs. This uses less server time.

The built-in changes are:

`HolderChange`	Occurs when
`Items`	The inventory, the armour, or the held item changes.
`Respawn`	The player respawns.
`WorldChange`	The player goes to a different world.
`custom<E> { event -> dispatcher }`	A Bukkit event of type `E` occurs. Return the dispatcher to check, or `null` to ignore the event.

// Check again only when the player changes game mode.
override val invalidatedBy = setOf(
    HolderChange.custom<PlayerGameModeChangeEvent> { it.player.toDispatcher() }
)

Caution: If you set invalidatedBy, it must contain every change that can change the result. If it does not, a permanent effect can stay on when the condition is false.

Note: A condition that reads a placeholder from a config is always checked at the fixed interval. Placeholders can change at any time.

Things to know

Triggered effects check their conditions each time the trigger occurs. invalidatedBy does not change this.
The user can write inverse: true and not-met-lines in the config. Libreforge does this for you.
Keep isMet fast. Libreforge calls it frequently.

Creating a Condition

Make a condition

When libreforge checks a condition

Things to know

Next steps