CachedPlayerKey

This section details the content and implementation of the CachedPlayerKey from a developer perspective.

The CachedPlayerKey is a type of key-wrapper hybrid. It serves to hold a generic type and provide a value of this type through a key-function map.

Structure¶

The CachedPlayerKey abstract class accepts a generic argument that represents its data type. For example, CachedPlayerKey<Integer> holds an Integer value. The interface has the following methods, where V denotes its generic type provided upon implementation of the class:

Implementation

FabricForge

Returned	Function	Description
`V?`	`get`	When the player is online, gets the value from the player. When the player disconnects, this is used to cache the value on the server. This may be nullable.
`V`	`readFromNbt`	Reads the value from `nbt`.
`void`	`writeToNbt`	Writes a value to a `nbt`.
`Identifier`	`id`	Returns the key's registered `Identifier`. An example would be `your_mod_id:your_key_name`.

Returned	Function	Description
`V?`	`get`	When the player is online, gets the value from the player. When the player disconnects, this is used to cache the value on the server. This may be nullable.
`V`	`readFromNbt`	Reads the value from `nbt`.
`void`	`writeToNbt`	Writes a value to a `nbt`.
`ResourceLocation`	`id`	Returns the key's registered `ResourceLocation`. An example would be `your_mod_id:your_key_name`.

Creating & Registering Your Key¶

For every value or piece of data that a mod wishes to cache, they must implement the CachedPlayerKey.

The following implementation goes through the process in creating a theoretical LevelKey.

Example

FabricForge

import com.bibireden.opc.api.CachedPlayerKey
import net.minecraft.nbt.NbtCompound
import net.minecraft.server.network.ServerPlayerEntity
import net.minecraft.util.Identifier

class LevelKey : CachedPlayerKey<Int>(Identifier("your-mod-id", "your-key-path")) {
    override fun get(player: ServerPlayerEntity): Int {
        // this would be up to the end user's interpretation, so for now, anything will suffice.
        return 404
    }

    override fun readFromNbt(tag: NbtCompound): Int {
        return tag.getInt("level")
    }

    override fun writeToNbt(tag: NbtCompound, value: Any) {
        // Due to some limitations, type checking cannot be provided for the second argument, but you can almost safely guarantee this value will be associated with your type-parameter.
        if (value is Int) tag.putInt("level", value)
    }
}

import com.bibireden.opc.api.CachedPlayerKey
import net.minecraft.nbt.CompoundTag
import net.minecraft.resources.ResourceLocation
import net.minecraft.world.entity.player.Player

class LevelKey : CachedPlayerKey<String>(ResourceLocation("your-mod-id", "your-key-path")) {
    override fun get(player: Player): String {
        // this would be up to the end user's interpretation, so for now, anything will suffice.
        return "playerex in forge when?"
    }

    override fun readFromNbt(tag: CompoundTag): String {
        return tag.getString("message")
    }

    override fun writeToNbt(tag: CompoundTag, value: Any) {
        tag.putString("message", value as String)
    }
}

Now it's time to register your key! It is ideal you call upon the OfflinePlayerCacheAPI's static register function in order to register the key properly.

ExampleMod.kt

val LEVEL_KEY = OfflinePlayerCacheAPI.register(LevelKey())

Notes¶

If you are needing to check for equality between your derived class, you can override the equals method. This is left to you to implement yourself, we do not guarantee the equality of your instances as it is user-dependent on how you wish to go about that.
You should try to ensure that the appropriate type is used in your generic. In the example above, Float is used because the return type of player#getHealth is a Float. Using Integer here would not be appropriate as you would lose data, and using Double here would also not be appropriate because the extra precision is not utilised.

Last update: 2024-05-23