View Source State

Nostrum keeps track of the state that your bot can see. This state is updated based on events from the WS connection. Most of the cache modules support only simple interactions with the cache. Feel free to suggest additional functionality.

Pluggable caches

The default caches supplied by nostrum should work for most of your needs, but all of the caches can be exchanged for your own implementations. For this, implement the behaviours exported by the cache modules under Nostrum.Cache.

Use the [:nostrum, :caches] configuration for configuring which cache implementation you want to use. This can only be set at dependency compilation time. A common situation is that you don't want to cache presences in your bot, most likely you don't care about user's status, so you can disable it altogether by using the NoOp presence cache:

config :nostrum,
  caches: %{
    presences: Nostrum.Cache.PresenceCache.NoOp
  }

Structs

Nostrum uses structs when appropriate to pass around objects from Discord.

In some cases, the struct modules will include helper functions for interacting with the struct. See Nostrum.Struct.Emoji.image_url/1 for an example.

Guilds

By default, guilds are cached in an ETS table, keyed off their ID. You can obtain the table name of the backing ETS table using the tabname function exported by the Nostrum.Cache.GuildCache.ETS module.

If you do not have the :guilds intent enabled, it is recommended to use the NoOp cache for guilds.

Please see Nostrum.Cache.GuildCache for more information on interacting with guilds.

Channels

By default, DM channels are stored in an ETS table, see Nostrum.Cache.ChannelCache.ETS. Guild channels are stored in their respective guilds.

Users

By default, users are all stored in an ETS table, keyed off of their id.

To see the name of the ETS table associated with the user cache, and examples of interacting with it both directly and through the provided abstractions, please see Nostrum.Cache.UserCache.ETS.

Mappings

There are some use cases where given a channel_id or guild_id we may want to find the guild or shard that the id belongs to. For this purpose Nostrum stores these types of relations in ETS tables.

The following mappings exists.

guild_channel_id -> guild_id
guild_id -> shard_num
shard_num_num -> shard_pid

Please see Nostrum.Cache.Mapping.ChannelGuild for one such map.