Struct bevy::ecs::component::ComponentDescriptor

pub struct ComponentDescriptor { /* private fields */ }

A value describing a component or resource, which may or may not correspond to a Rust type.

Implementations

impl ComponentDescriptor

pub fn new<T>() -> ComponentDescriptor

where T: Component,

Create a new ComponentDescriptor for the type T.

pub unsafe fn new_with_layout( name: impl Into<Cow<'static, str>>, storage_type: StorageType, layout: Layout, drop: Option<for<'a> unsafe fn(_: OwningPtr<'a>)> ) -> ComponentDescriptor

Create a new ComponentDescriptor.

Safety

• the drop fn must be usable on a pointer with a value of the layout layout
• the component type must be safe to access from any thread (Send + Sync in rust terms)

Examples found in repository

examples/ecs/dynamic.rs (lines 89-94)

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();

    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),
                _ => 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(|s| s.parse::<usize>()) {
                        Some(Ok(size)) => size,
                        _ => 0,
                    };
                    // Register our new component to the world with a layout specified by it's size
                    // SAFETY: [u64] is Send + Sync
                    let id = world.init_component_with_descriptor(unsafe {
                        ComponentDescriptor::new_with_layout(
                            name.to_string(),
                            StorageType::Table,
                            Layout::array::<u64>(size).unwrap(),
                            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 {} does not exist", name);
                        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() / std::mem::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
                        .components()
                        .map(|id| {
                            let ptr = filtered_entity.get_by_id(id).unwrap();
                            let info = component_info.get(&id).unwrap();
                            let len = info.layout().size() / std::mem::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 filtered_entity.access().has_write(id) {
                                data.iter_mut().for_each(|data| {
                                    *data += 1;
                                });
                            }

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

                    println!("{:?}: {}", filtered_entity.id(), terms);
                });
            }
            _ => continue,
        }
    }
}

pub fn new_resource<T>() -> ComponentDescriptor

where T: Resource,

Create a new ComponentDescriptor for a resource.

The StorageType for resources is always StorageType::Table.

pub fn storage_type(&self) -> StorageType

Returns a value indicating the storage strategy for the current component.

pub fn type_id(&self) -> Option<TypeId>

Returns the TypeId of the underlying component type. Returns None if the component does not correspond to a Rust type.

pub fn name(&self) -> &str

Returns the name of the current component.

Trait Implementations

impl Clone for ComponentDescriptor

fn clone(&self) -> ComponentDescriptor

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ComponentDescriptor

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

Formats the value using the given formatter.