Struct serenity::cache::Cache

#[non_exhaustive]pub struct Cache { /* fields omitted */ }

A cache containing data received from Shards.

Using the cache allows to avoid REST API requests via the http module where possible. Issuing too many requests will lead to ratelimits.

The cache will clone all values when calling its methods.

Implementations

impl Cache

pub fn new() -> Self

Creates a new cache.

pub fn new_with_settings(settings: Settings) -> Self

Creates a new cache instance with settings applied.

Examples

use serenity::cache::{Cache, Settings};

let mut settings = Settings::new();
settings.max_messages(10);

let cache = Cache::new_with_settings(settings);

pub async fn unknown_members<'_>(&'_ self) -> u64

Fetches the number of Members that have not had data received.

The important detail to note here is that this is the number of _member_s that have not had data received. A single User may have multiple associated member objects that have not been received.

This can be used in combination with Shard::chunk_guild, and can be used to determine how many members have not yet been received.

use std::thread;
use std::time::Duration;

struct Handler;

#[serenity::async_trait]
impl EventHandler for Handler {
    async fn ready(&self, ctx: Context, _: Ready) {
        // Wait some time for guilds to be received.
        //
        // You should keep track of this in a better fashion by tracking how
        // many guilds each `ready` has, and incrementing a counter on
        // GUILD_CREATEs. Once the number is equal, print the number of
        // unknown members.
        //
        // For demonstrative purposes we're just sleeping the thread for 5
        // seconds.
        tokio::time::delay_for(Duration::from_secs(5)).await;

        println!("{} unknown members", ctx.cache.unknown_members().await);
    }
}

let mut client =Client::builder("token").event_handler(Handler).await?;

client.start().await?;

pub async fn private_channels<'_>(
    &'_ self
) -> HashMap<ChannelId, PrivateChannel>

Fetches a vector of all PrivateChannel Ids that are stored in the cache.

Examples

If there are 6 private channels and 2 groups in the cache, then 8 Ids will be returned.

Printing the count of all private channels and groups:

let amount = cache.private_channels().await.len();

println!("There are {} private channels", amount);

pub async fn guilds<'_>(&'_ self) -> Vec<GuildId>

Fetches a vector of all Guilds' Ids that are stored in the cache.

Note that if you are utilizing multiple Shards, then the guilds retrieved over all shards are included in this count -- not just the current Context's shard, if accessing from one.

Examples

Print all of the Ids of guilds in the Cache:

struct Handler;

#[serenity::async_trait]
impl EventHandler for Handler {
    async fn ready(&self, context: Context, _: Ready) {
        let guilds = context.cache.guilds().await.len();

        println!("Guilds in the Cache: {}", guilds);
    }
}

pub async fn channel<C: Into<ChannelId>, '_>(&'_ self, id: C) -> Option<Channel>

Retrieves a Channel from the cache based on the given Id.

This will search the channels map, then the private_channels map.

If you know what type of channel you're looking for, you should instead manually retrieve from one of the respective maps or methods:

• GuildChannel: guild_channel or channels
• PrivateChannel: private_channel or private_channels

pub async fn guild<G: Into<GuildId>, '_>(&'_ self, id: G) -> Option<Guild>

Clones an entire guild from the cache based on the given id.

In order to clone only a field of the guild, use guild_field.

Examples

Retrieve a guild from the cache and print its name:

// assuming the cache is in scope, e.g. via `Context`
if let Some(guild) = cache.guild(7).await {
    println!("Guild name: {}", guild.name);
}

pub async fn guild_field<Ret, Fun, '_>(
    &'_ self,
    id: impl Into<GuildId>,
    field_selector: Fun
) -> Option<Ret> where
    Fun: FnOnce(&Guild) -> Ret, 

This method allows to select a field of the guild instead of the entire guild by providing a field_selector-closure picking what you want to clone.

// We clone only the `len()` returned `usize` instead of the entire guild or the channels.
if let Some(channel_len) = cache.guild_field(7, |guild| guild.channels.len()).await {
    println!("Guild channels count: {}", channel_len);
}

pub async fn guild_count<'_>(&'_ self) -> usize

Returns the number of cached guilds.

pub async fn guild_channel<C: Into<ChannelId>, '_>(
    &'_ self,
    id: C
) -> Option<GuildChannel>

Retrieves a reference to a Guild's channel. Unlike channel, this will only search guilds for the given channel.

The only advantage of this method is that you can pass in anything that is indirectly a ChannelId.

Examples

Getting a guild's channel via the Id of the message received through a Client::on_message event dispatch:

struct Handler;

#[serenity::async_trait]
impl EventHandler for Handler {
    async fn message(&self, context: Context, message: Message) {

        let channel = match context.cache.guild_channel(message.channel_id).await {
            Some(channel) => channel,
            None => {
                let result = message.channel_id.say(&context, "Could not find guild's channel data").await;
                if let Err(why) = result {
                    println!("Error sending message: {:?}", why);
                }

                return;
            },
        };
    }
}

let mut client =Client::builder("token").event_handler(Handler).await?;

client.start().await?;

pub async fn guild_channel_field<Ret, Fun, '_>(
    &'_ self,
    id: impl Into<ChannelId>,
    field_selector: Fun
) -> Option<Ret> where
    Fun: FnOnce(&GuildChannel) -> Ret, 

This method allows to only clone a field of the guild channel instead of the entire guild by providing a field_selector-closure picking what you want to clone.

// We clone only the `name` instead of the entire channel.
if let Some(channel_name) = cache.guild_channel_field(7, |channel| channel.name.clone()).await {
    println!("Guild channel name: {}", channel_name);
}

pub async fn member<G, U, '_>(
    &'_ self,
    guild_id: G,
    user_id: U
) -> Option<Member> where
    G: Into<GuildId>,
    U: Into<UserId>, 

Retrieves a Guild's member from the cache based on the guild's and user's given Ids.

Note: This will clone the entire member. Instead, retrieve the guild and retrieve from the guild's members map to avoid this.

Examples

Retrieving the member object of the user that posted a message, in a Client::on_message context:

let member = {
    let channel = match cache.guild_channel(message.channel_id).await {
        Some(channel) => channel,
        None => {
            if let Err(why) = message.channel_id.say(http, "Error finding channel data").await {
                println!("Error sending message: {:?}", why);
            }
            return;
        },
    };

    match cache.member(channel.guild_id, message.author.id).await {
        Some(member) => member,
        None => {
            if let Err(why) = message.channel_id.say(&http, "Error finding member data").await {
                println!("Error sending message: {:?}", why);
            }
            return;
        },
    }
};

let msg = format!("You have {} roles", member.roles.len());

if let Err(why) = message.channel_id.say(&http, &msg).await {
    println!("Error sending message: {:?}", why);
}

pub async fn member_field<Ret, Fun, '_>(
    &'_ self,
    guild_id: impl Into<GuildId>,
    user_id: impl Into<UserId>,
    field_selector: Fun
) -> Option<Ret> where
    Fun: FnOnce(&Member) -> Ret, 

This method allows to only clone a field of a member instead of the entire member by providing a field_selector-closure picking what you want to clone.

// We clone only the `name` instead of the entire channel.
if let Some(Some(nick)) = cache.member_field(7, 8, |member| member.nick.clone()).await {
    println!("Member's nick: {}", nick);
}

pub async fn guild_roles<'_>(
    &'_ self,
    guild_id: impl Into<GuildId>
) -> Option<HashMap<RoleId, Role>>

pub async fn unavailable_guilds<'_>(&'_ self) -> HashSet<GuildId>

This method clones and returns all unavailable guilds.

pub async fn guild_channels<'_>(
    &'_ self,
    guild_id: impl Into<GuildId>
) -> Option<HashMap<ChannelId, GuildChannel>>

This method returns all channels from a guild of with the given guild_id.

pub async fn guild_channel_count<'_>(&'_ self) -> usize

Returns the number of guild channels in the cache.

pub async fn shard_count<'_>(&'_ self) -> u64

Returns the number of shards.

pub async fn message<C, M, '_>(
    &'_ self,
    channel_id: C,
    message_id: M
) -> Option<Message> where
    C: Into<ChannelId>,
    M: Into<MessageId>, 

Retrieves a Channel's message from the cache based on the channel's and message's given Ids.

Note: This will clone the entire message.

Examples

Retrieving the message object from a channel, in a EventHandler::message context:

match cache.message(message.channel_id, message.id).await {
    Some(m) => assert_eq!(message.content, m.content),
    None =>println!("No message found in cache."),
};

pub async fn private_channel<'_>(
    &'_ self,
    channel_id: impl Into<ChannelId>
) -> Option<PrivateChannel>

Retrieves a PrivateChannel from the cache's private_channels map, if it exists.

The only advantage of this method is that you can pass in anything that is indirectly a ChannelId.

Examples

Retrieve a private channel from the cache and print its recipient's name:

// assuming the cache has been unlocked

if let Some(channel) = cache.private_channel(7).await {
    println!("The recipient is {}", channel.recipient);
}

pub async fn role<G, R, '_>(&'_ self, guild_id: G, role_id: R) -> Option<Role> where
    G: Into<GuildId>,
    R: Into<RoleId>, 

Retrieves a Guild's role by their Ids.

Note: This will clone the entire role. Instead, retrieve the guild and retrieve from the guild's roles map to avoid this.

Examples

Retrieve a role from the cache and print its name:

// assuming the cache is in scope, e.g. via `Context`
if let Some(role) = cache.role(7, 77).await {
    println!("Role with Id 77 is called {}", role.name);
}

pub async fn settings<'_>(&'_ self) -> Settings

Returns the settings.

Examples

Printing the maximum number of messages in a channel to be cached:

use serenity::cache::Cache;

let mut cache = Cache::new();
println!("Max settings: {}", cache.settings().await.max_messages);

pub async fn set_max_messages<'_>(&'_ self, max: usize)

Sets the maximum amount of messages per channel to cache.

By default, no messages will be cached.

pub async fn user<U: Into<UserId>, '_>(&'_ self, user_id: U) -> Option<User>

Retrieves a User from the cache's users map, if it exists.

The only advantage of this method is that you can pass in anything that is indirectly a UserId.

Examples

Retrieve a user from the cache and print their name:

if let Some(user) = context.cache.user(7).await {
    println!("User with Id 7 is currently named {}", user.name);
}

pub async fn users<'_>(&'_ self) -> HashMap<UserId, User>

Clones all users and returns them.

pub async fn user_count<'_>(&'_ self) -> usize

Returns the amount of cached users.

pub async fn category<C: Into<ChannelId>, '_>(
    &'_ self,
    channel_id: C
) -> Option<ChannelCategory>

Clones a category matching the channel_id and returns it.

pub async fn categories<'_>(&'_ self) -> HashMap<ChannelId, ChannelCategory>

Clones all categories and returns them.

pub async fn category_count<'_>(&'_ self) -> usize

Returns the amount of cached categories.

pub async fn current_user<'_>(&'_ self) -> CurrentUser

This method clones and returns the user used by the bot.

pub async fn current_user_id<'_>(&'_ self) -> UserId

This method returns the bot's ID.

pub async fn current_user_field<Ret: Clone, Fun, '_>(
    &'_ self,
    field_selector: Fun
) -> Ret where
    Fun: FnOnce(&CurrentUser) -> Ret, 

This method allows to only clone a field of the current user instead of the entire user by providing a field_selector-closure picking what you want to clone.

// We clone only the `name` instead of the entire channel.
let id = cache.current_user_field(|user| user.id).await;
println!("Current user's ID: {}", id);

pub async fn update<E: CacheUpdate, '_, '_>(
    &'_ self,
    e: &'_ mut E
) -> Option<E::Output>

Updates the cache with the update implementation for an event or other custom update implementation.

Refer to the documentation for CacheUpdate for more information.

Examples

Refer to the CacheUpdate examples.

Trait Implementations

impl AsRef<Cache> for Context

fn as_ref(&self) -> &Cache

Performs the conversion.

impl AsRef<Cache> for Arc<Context>

fn as_ref(&self) -> &Cache

Performs the conversion.

impl AsRef<Cache> for Cache

fn as_ref(&self) -> &Cache

Performs the conversion.

impl<'_, '_> AsRef<Cache> for (&'_ Arc<Cache>, &'_ Http)

fn as_ref(&self) -> &Cache

Performs the conversion.

impl Debug for Cache

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Cache

fn default() -> Cache

Returns the "default value" for a type.