Type Definition specs::storage::WriteStorage

type WriteStorage<'a, T> = Storage<'a, T, FetchMut<'a, MaskedStorage<T>>>;

A storage with read and write access.

Additionally to what ReadStorage can do a storage with mutable access allows:

Aliasing

It is strictly disallowed to fetch both a ReadStorage and a WriteStorage of the same component. Because Specs uses interior mutability for its resources, we can't check this at compile time. If you try to do this, you will get a panic.

It is also disallowed to fetch multiple WriteStorages for the same component.

Retrieve components mutably

This works just like Storage::get, but returns a mutable reference:

let entity = world.create_entity()
    .with(Pos(2.0))
    .build();

assert_eq!(pos_storage.get_mut(entity), Some(&mut Pos(2.0)));
if let Some(pos) = pos_storage.get_mut(entity) {
    *pos = Pos(4.5);
}

assert_eq!(pos_storage.get(entity), Some(&Pos(4.5)));

Inserting and removing components

You can insert components using Storage::insert and remove them again with Storage::remove.

let entity = world.create_entity()
    .with(Pos(0.1))
    .build();

let res = pos_storage.insert(entity, Pos(4.0));
assert_eq!(res, InsertResult::Updated(Pos(0.1)));

There's also an Entry-API similar to the one provided by std::collections::HashMap.

Trait Implementations

impl<'a, T> SystemData<'a> for WriteStorage<'a, T> where
    T: Component, 

fn fetch(res: &'a Resources) -> Self

Creates a new resource bundle by fetching the required resources from the [Resources] struct.

Important traits for Vec<u8>

impl Write for Vec<u8>

fn reads() -> Vec<ResourceId>

A list of [ResourceId]s the bundle needs read access to in order to build the target resource bundle.

Important traits for Vec<u8>

impl Write for Vec<u8>

fn writes() -> Vec<ResourceId>

A list of [ResourceId]s the bundle needs write access to in order to build the target resource bundle.

fn setup(res: &mut Resources)

Sets up Resources for fetching this system data.