Struct Components 

pub struct Components { /* private fields */ }

Stores metadata associated with each kind of Component in a given World.

Implementations

impl Components

pub fn len(&self) -> usize

Returns the number of components registered or queued with this instance.

pub fn is_empty(&self) -> bool

Returns true if there are no components registered or queued with this instance. Otherwise, this returns false.

pub fn num_queued(&self) -> usize

Returns the number of components registered with this instance.

pub fn any_queued(&self) -> bool

Returns true if there are any components registered with this instance. Otherwise, this returns false.

pub fn num_queued_mut(&mut self) -> usize

A faster version of Self::num_queued.

pub fn any_queued_mut(&mut self) -> bool

A faster version of Self::any_queued.

pub fn num_registered(&self) -> usize

Returns the number of components registered with this instance.

pub fn any_registered(&self) -> bool

Returns true if there are any components registered with this instance. Otherwise, this returns false.

pub fn get_info(&self, id: ComponentId) -> Option<&ComponentInfo>

Gets the metadata associated with the given component, if it is registered. This will return None if the id is not registered or is queued.

This will return an incorrect result if id did not come from the same world as self. It may return None or a garbage value.

Examples found in repository

examples/ecs/dynamic.rs (line 125)

fn main() {
    let mut world = World::new();
    let mut lines = std::io::stdin().lines();
    let mut component_names = HashMap::<String, ComponentId>::new();
    let mut component_info = HashMap::<ComponentId, ComponentInfo>::new();
    let mut event_names = HashMap::<String, EventKey>::new();

    println!("{PROMPT}");
    loop {
        print!("\n> ");
        let _ = std::io::stdout().flush();
        let Some(Ok(line)) = lines.next() else {
            return;
        };

        if line.is_empty() {
            return;
        };

        let Some((first, rest)) = line.trim().split_once(|c: char| c.is_whitespace()) else {
            match &line.chars().next() {
                Some('c') => println!("{COMPONENT_PROMPT}"),
                Some('s') => println!("{ENTITY_PROMPT}"),
                Some('q') => println!("{QUERY_PROMPT}"),
                Some('e') => println!("{EVENT_PROMPT}"),
                Some('t') => println!("{EMIT_PROMPT}"),
                _ => println!("{PROMPT}"),
            }
            continue;
        };

        match &first[0..1] {
            "c" => {
                rest.split(',').for_each(|component| {
                    let mut component = component.split_whitespace();
                    let Some(name) = component.next() else {
                        return;
                    };
                    let size = match component.next().map(str::parse) {
                        Some(Ok(size)) => size,
                        _ => 0,
                    };
                    // Register our new component to the world with a layout specified by its size
                    // SAFETY: [u64] is Send + Sync
                    let id = world.register_component_with_descriptor(unsafe {
                        ComponentDescriptor::new_with_layout(
                            name.to_string(),
                            StorageType::Table,
                            Layout::array::<u64>(size).unwrap(),
                            None,
                            true,
                            false,
                            ComponentCloneBehavior::Default,
                            None,
                        )
                    });
                    let Some(info) = world.components().get_info(id) else {
                        return;
                    };
                    component_names.insert(name.to_string(), id);
                    component_info.insert(id, info.clone());
                    println!("Component {} created with id: {}", name, id.index());
                });
            }
            "s" => {
                let mut to_insert_ids = Vec::new();
                let mut to_insert_data = Vec::new();
                rest.split(',').for_each(|component| {
                    let mut component = component.split_whitespace();
                    let Some(name) = component.next() else {
                        return;
                    };

                    // Get the id for the component with the given name
                    let Some(&id) = component_names.get(name) else {
                        println!("Component {name} does not exist");
                        return;
                    };

                    // Calculate the length for the array based on the layout created for this component id
                    let info = world.components().get_info(id).unwrap();
                    let len = info.layout().size() / size_of::<u64>();
                    let mut values: Vec<u64> = component
                        .take(len)
                        .filter_map(|value| value.parse::<u64>().ok())
                        .collect();
                    values.resize(len, 0);

                    // Collect the id and array to be inserted onto our entity
                    to_insert_ids.push(id);
                    to_insert_data.push(values);
                });

                let mut entity = world.spawn_empty();

                // Construct an `OwningPtr` for each component in `to_insert_data`
                let to_insert_ptr = to_owning_ptrs(&mut to_insert_data);

                // SAFETY:
                // - Component ids have been taken from the same world
                // - Each array is created to the layout specified in the world
                unsafe {
                    entity.insert_by_ids(&to_insert_ids, to_insert_ptr.into_iter());
                }

                println!("Entity spawned with id: {}", entity.id());
            }
            "q" => {
                let mut builder = QueryBuilder::<FilteredEntityMut>::new(&mut world);
                parse_query(rest, &mut builder, &component_names);
                let mut query = builder.build();
                query.iter_mut(&mut world).for_each(|filtered_entity| {
                    let terms = filtered_entity
                        .access()
                        .try_iter_access()
                        .unwrap()
                        .map(|component_access| {
                            let id = *component_access.index();
                            let ptr = filtered_entity.get_by_id(id).unwrap();
                            let info = component_info.get(&id).unwrap();
                            let len = info.layout().size() / size_of::<u64>();

                            // SAFETY:
                            // - All components are created with layout [u64]
                            // - len is calculated from the component descriptor
                            let data = unsafe {
                                std::slice::from_raw_parts_mut(
                                    ptr.assert_unique().as_ptr().cast::<u64>(),
                                    len,
                                )
                            };

                            // If we have write access, increment each value once
                            if matches!(component_access, ComponentAccessKind::Exclusive(_)) {
                                data.iter_mut().for_each(|data| {
                                    *data += 1;
                                });
                            }

                            format!("{}: {:?}", info.name(), data[0..len].to_vec())
                        })
                        .collect::<Vec<_>>()
                        .join(", ");

                    println!("{}: {}", filtered_entity.id(), terms);
                });
            }
            "e" => {
                rest.split(',').for_each(|event| {
                    let name = event.trim();
                    if name.is_empty() {
                        return;
                    }

                    // Register a ComponentId for this event, no Rust type needed.
                    // SAFETY: ZST with no drop
                    let event_component_id = world.register_component_with_descriptor(unsafe {
                        ComponentDescriptor::new_with_layout(
                            format!("event:{name}"),
                            StorageType::Table,
                            Layout::new::<()>(),
                            None,
                            false,
                            false,
                            ComponentCloneBehavior::Ignore,
                            None,
                        )
                    });
                    // SAFETY: event_component_id was just registered for this event
                    let event_key = unsafe { EventKey::new(event_component_id) };
                    event_names.insert(name.to_string(), event_key);

                    // Build a dynamic observer that prints when the event fires.
                    let runner: ObserverRunner = |mut world, _observer, ctx, _event, _trigger| {
                        println!("  Observer fired!");
                        if let Some(mut counts) = world.get_resource_mut::<EventFireCount>() {
                            *counts.0.entry(ctx.event_key).or_insert(0) += 1;
                        }
                    };

                    // SAFETY: event_key was just registered, runner ignores pointers
                    let observer =
                        unsafe { Observer::with_dynamic_runner(runner).with_event_key(event_key) };
                    world.spawn(observer);

                    println!(
                        "Event '{name}' registered (key: {}) with a dynamic observer",
                        event_component_id.index()
                    );
                });

                // Ensure the counter resource exists.
                world.init_resource::<EventFireCount>();
            }
            "t" => {
                let name = rest.trim();
                let Some(&event_key) = event_names.get(name) else {
                    println!(
                        "Event '{name}' does not exist. Register it first with 'event {name}'"
                    );
                    continue;
                };

                let mut event_data = ();
                let mut trigger_data = ();
                // SAFETY: event_key was registered in this world, both pointers are valid ZSTs
                unsafe {
                    world.trigger_dynamic(
                        event_key,
                        PtrMut::from(&mut event_data),
                        PtrMut::from(&mut trigger_data),
                    );
                }

                let count = world
                    .get_resource::<EventFireCount>()
                    .map_or(0, |c| c.0.get(&event_key).copied().unwrap_or(0));
                println!("Event '{name}' triggered ({count} fires)");
            }
            _ => continue,
        }
    }
}

pub fn get_descriptor<'a>( &'a self, id: ComponentId, ) -> Option<Cow<'a, ComponentDescriptor>>

Gets the ComponentDescriptor of the component with this ComponentId if it is present. This will return None only if the id is neither registered nor queued to be registered.

Currently, the Cow will be Cow::Owned if and only if the component is queued. It will be Cow::Borrowed otherwise.

This will return an incorrect result if id did not come from the same world as self. It may return None or a garbage value.

pub fn get_name<'a>(&'a self, id: ComponentId) -> Option<DebugName>

Gets the name of the component with this ComponentId if it is present. This will return None only if the id is neither registered nor queued to be registered.

This will return an incorrect result if id did not come from the same world as self. It may return None or a garbage value.

pub unsafe fn get_info_unchecked(&self, id: ComponentId) -> &ComponentInfo

Gets the metadata associated with the given component.

Safety

id must be a valid and fully registered ComponentId.

pub fn is_id_valid(&self, id: ComponentId) -> bool

Returns true if the ComponentId is fully registered and valid. Ids may be invalid if they are still queued to be registered. Those ids are still correct, but they are not usable in every context yet.

pub fn get_valid_id(&self, type_id: TypeId) -> Option<ComponentId>

Type-erased equivalent of Components::valid_component_id().

pub fn valid_component_id<T>(&self) -> Option<ComponentId>

where T: Component,

Returns the ComponentId of the given Component type T if it is fully registered. If you want to include queued registration, see Components::component_id().

use bevy_ecs::prelude::*;

let mut world = World::new();

#[derive(Component)]
struct ComponentA;

let component_a_id = world.register_component::<ComponentA>();

assert_eq!(component_a_id, world.components().valid_component_id::<ComponentA>().unwrap())

See also

• Components::get_valid_id()
• World::component_id()

pub fn get_id(&self, type_id: TypeId) -> Option<ComponentId>

Type-erased equivalent of Components::component_id().

pub fn component_id<T>(&self) -> Option<ComponentId>

where T: Component,

Returns the ComponentId of the given Component type T.

The returned ComponentId is specific to the Components instance it was retrieved from and should not be used with another Components instance.

Returns None if the Component type has not yet been initialized using ComponentsRegistrator::register_component() or ComponentsQueuedRegistrator::queue_register_component().

use bevy_ecs::prelude::*;

let mut world = World::new();

#[derive(Component)]
struct ComponentA;

let component_a_id = world.register_component::<ComponentA>();

assert_eq!(component_a_id, world.components().component_id::<ComponentA>().unwrap())

See also

• ComponentIdFor
• Components::get_id()
• World::component_id()

pub fn iter_registered( &self, ) -> impl Iterator<Item = (ComponentId, &ComponentInfo)>

Gets an iterator over all components fully registered with this instance.

Trait Implementations

impl Debug for Components

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

Formats the value using the given formatter.

impl Default for Components

fn default() -> Components

Returns the “default value” for a type.

impl<'a> ReadOnlySystemParam for &'a Components

impl<'a> SystemParam for &'a Components

type State = ()

Used to store data which persists across invocations of a system.

type Item<'w, 's> = &'w Components

The item type returned when constructing this system param. The value of this associated type should be Self, instantiated with new lifetimes.

fn init_state(_world: &mut World) -> <&'a Components as SystemParam>::State

Creates a new instance of this param’s State.

fn init_access( _state: &<&'a Components as SystemParam>::State, system_meta: &mut SystemMeta, system_access: &mut SystemAccess, _world: &mut World, )

Registers any World access used by this SystemParam.

unsafe fn get_param<'w, 's>( _state: &'s mut <&'a Components as SystemParam>::State, _system_meta: &SystemMeta, world: UnsafeWorldCell<'w>, _change_tick: Tick, ) -> Result<<&'a Components as SystemParam>::Item<'w, 's>, SystemParamValidationError>

Creates a parameter to be passed into a SystemParamFunction.

fn apply(state: &mut Self::State, system_meta: &SystemMeta, world: &mut World)

Applies any deferred mutations stored in this SystemParam’s state. This is used to apply Commands during ApplyDeferred.

fn queue( state: &mut Self::State, system_meta: &SystemMeta, world: DeferredWorld<'_>, )

Queues any deferred mutations to be applied at the next ApplyDeferred.