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Add methods iter_resources and iter_resources_mut (#12829)
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# Objective

- Closes #12019
- Related to #4955
- Useful for dev_tools and networking

## Solution

- Create `World::iter_resources()` and `World::iter_resources_mut()`

---------

Co-authored-by: Alice Cecile <[email protected]>
Co-authored-by: James Liu <[email protected]>
Co-authored-by: Pablo Reinhardt <[email protected]>
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@matiqo15 @alice-i-cecile
@james7132 @pablo-lua
4 people authored Apr 3, 2024
1 parent 257df3a commit 1d4176d
Showing 1 changed file with 269 additions and 0 deletions.
269 changes: 269 additions & 0 deletions crates/bevy_ecs/src/world/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2136,6 +2136,209 @@ impl World {
}
}

/// Iterates over all resources in the world.
///
/// The returned iterator provides lifetimed, but type-unsafe pointers. Actually reading the contents
/// of each resource will require the use of unsafe code.
///
/// # Examples
///
/// ## Printing the size of all resources
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # #[derive(Resource)]
/// # struct A(u32);
/// # #[derive(Resource)]
/// # struct B(u32);
/// #
/// # let mut world = World::new();
/// # world.insert_resource(A(1));
/// # world.insert_resource(B(2));
/// let mut total = 0;
/// for (info, _) in world.iter_resources() {
/// println!("Resource: {}", info.name());
/// println!("Size: {} bytes", info.layout().size());
/// total += info.layout().size();
/// }
/// println!("Total size: {} bytes", total);
/// # assert_eq!(total, std::mem::size_of::<A>() + std::mem::size_of::<B>());
/// ```
///
/// ## Dynamically running closures for resources matching specific `TypeId`s
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # use std::collections::HashMap;
/// # use std::any::TypeId;
/// # use bevy_ptr::Ptr;
/// # #[derive(Resource)]
/// # struct A(u32);
/// # #[derive(Resource)]
/// # struct B(u32);
/// #
/// # let mut world = World::new();
/// # world.insert_resource(A(1));
/// # world.insert_resource(B(2));
/// #
/// // In this example, `A` and `B` are resources. We deliberately do not use the
/// // `bevy_reflect` crate here to showcase the low-level [`Ptr`] usage. You should
/// // probably use something like `ReflectFromPtr` in a real-world scenario.
///
/// // Create the hash map that will store the closures for each resource type
/// let mut closures: HashMap<TypeId, Box<dyn Fn(&Ptr<'_>)>> = HashMap::new();
///
/// // Add closure for `A`
/// closures.insert(TypeId::of::<A>(), Box::new(|ptr| {
/// // SAFETY: We assert ptr is the same type of A with TypeId of A
/// let a = unsafe { &ptr.deref::<A>() };
/// # assert_eq!(a.0, 1);
/// // ... do something with `a` here
/// }));
///
/// // Add closure for `B`
/// closures.insert(TypeId::of::<B>(), Box::new(|ptr| {
/// // SAFETY: We assert ptr is the same type of B with TypeId of B
/// let b = unsafe { &ptr.deref::<B>() };
/// # assert_eq!(b.0, 2);
/// // ... do something with `b` here
/// }));
///
/// // Iterate all resources, in order to run the closures for each matching resource type
/// for (info, ptr) in world.iter_resources() {
/// let Some(type_id) = info.type_id() else {
/// // It's possible for resources to not have a `TypeId` (e.g. non-Rust resources
/// // dynamically inserted via a scripting language) in which case we can't match them.
/// continue;
/// };
///
/// let Some(closure) = closures.get(&type_id) else {
/// // No closure for this resource type, skip it.
/// continue;
/// };
///
/// // Run the closure for the resource
/// closure(&ptr);
/// }
/// ```
#[inline]
pub fn iter_resources(&self) -> impl Iterator<Item = (&ComponentInfo, Ptr<'_>)> {
self.storages
.resources
.iter()
.filter_map(|(component_id, data)| {
// SAFETY: If a resource has been initialized, a corresponding ComponentInfo must exist with it's ID.
let component_info = unsafe {
self.components
.get_info(component_id)
.debug_checked_unwrap()
};
Some((component_info, data.get_data()?))
})
}

/// Mutably iterates over all resources in the world.
///
/// The returned iterator provides lifetimed, but type-unsafe pointers. Actually reading from or writing
/// to the contents of each resource will require the use of unsafe code.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_ecs::change_detection::MutUntyped;
/// # use std::collections::HashMap;
/// # use std::any::TypeId;
/// # #[derive(Resource)]
/// # struct A(u32);
/// # #[derive(Resource)]
/// # struct B(u32);
/// #
/// # let mut world = World::new();
/// # world.insert_resource(A(1));
/// # world.insert_resource(B(2));
/// #
/// // In this example, `A` and `B` are resources. We deliberately do not use the
/// // `bevy_reflect` crate here to showcase the low-level `MutUntyped` usage. You should
/// // probably use something like `ReflectFromPtr` in a real-world scenario.
///
/// // Create the hash map that will store the mutator closures for each resource type
/// let mut mutators: HashMap<TypeId, Box<dyn Fn(&mut MutUntyped<'_>)>> = HashMap::new();
///
/// // Add mutator closure for `A`
/// mutators.insert(TypeId::of::<A>(), Box::new(|mut_untyped| {
/// // Note: `MutUntyped::as_mut()` automatically marks the resource as changed
/// // for ECS change detection, and gives us a `PtrMut` we can use to mutate the resource.
/// // SAFETY: We assert ptr is the same type of A with TypeId of A
/// let a = unsafe { &mut mut_untyped.as_mut().deref_mut::<A>() };
/// # a.0 += 1;
/// // ... mutate `a` here
/// }));
///
/// // Add mutator closure for `B`
/// mutators.insert(TypeId::of::<B>(), Box::new(|mut_untyped| {
/// // SAFETY: We assert ptr is the same type of B with TypeId of B
/// let b = unsafe { &mut mut_untyped.as_mut().deref_mut::<B>() };
/// # b.0 += 1;
/// // ... mutate `b` here
/// }));
///
/// // Iterate all resources, in order to run the mutator closures for each matching resource type
/// for (info, mut mut_untyped) in world.iter_resources_mut() {
/// let Some(type_id) = info.type_id() else {
/// // It's possible for resources to not have a `TypeId` (e.g. non-Rust resources
/// // dynamically inserted via a scripting language) in which case we can't match them.
/// continue;
/// };
///
/// let Some(mutator) = mutators.get(&type_id) else {
/// // No mutator closure for this resource type, skip it.
/// continue;
/// };
///
/// // Run the mutator closure for the resource
/// mutator(&mut mut_untyped);
/// }
/// # assert_eq!(world.resource::<A>().0, 2);
/// # assert_eq!(world.resource::<B>().0, 3);
/// ```
#[inline]
pub fn iter_resources_mut(&mut self) -> impl Iterator<Item = (&ComponentInfo, MutUntyped<'_>)> {
self.storages
.resources
.iter()
.filter_map(|(component_id, data)| {
// SAFETY: If a resource has been initialized, a corresponding ComponentInfo must exist with it's ID.
let component_info = unsafe {
self.components
.get_info(component_id)
.debug_checked_unwrap()
};
let (ptr, ticks) = data.get_with_ticks()?;

// SAFETY:
// - We have exclusive access to the world, so no other code can be aliasing the `TickCells`
// - We only hold one `TicksMut` at a time, and we let go of it before getting the next one
let ticks = unsafe {
TicksMut::from_tick_cells(
ticks,
self.last_change_tick(),
self.read_change_tick(),
)
};

let mut_untyped = MutUntyped {
// SAFETY:
// - We have exclusive access to the world, so no other code can be aliasing the `Ptr`
// - We iterate one resource at a time, and we let go of each `PtrMut` before getting the next one
value: unsafe { ptr.assert_unique() },
ticks,
};

Some((component_info, mut_untyped))
})
}

/// Gets a `!Send` resource to the resource with the id [`ComponentId`] if it exists.
/// The returned pointer must not be used to modify the resource, and must not be
/// dereferenced after the immutable borrow of the [`World`] ends.
Expand Down Expand Up @@ -2554,6 +2757,12 @@ mod tests {
#[derive(Resource)]
struct TestResource(u32);

#[derive(Resource)]
struct TestResource2(String);

#[derive(Resource)]
struct TestResource3;

#[test]
fn get_resource_by_id() {
let mut world = World::new();
Expand Down Expand Up @@ -2594,6 +2803,66 @@ mod tests {
assert_eq!(resource.0, 43);
}

#[test]
fn iter_resources() {
let mut world = World::new();
world.insert_resource(TestResource(42));
world.insert_resource(TestResource2("Hello, world!".to_string()));
world.insert_resource(TestResource3);
world.remove_resource::<TestResource3>();

let mut iter = world.iter_resources();

let (info, ptr) = iter.next().unwrap();
assert_eq!(info.name(), std::any::type_name::<TestResource>());
// SAFETY: We know that the resource is of type `TestResource`
assert_eq!(unsafe { ptr.deref::<TestResource>().0 }, 42);

let (info, ptr) = iter.next().unwrap();
assert_eq!(info.name(), std::any::type_name::<TestResource2>());
assert_eq!(
// SAFETY: We know that the resource is of type `TestResource2`
unsafe { &ptr.deref::<TestResource2>().0 },
&"Hello, world!".to_string()
);

assert!(iter.next().is_none());
}

#[test]
fn iter_resources_mut() {
let mut world = World::new();
world.insert_resource(TestResource(42));
world.insert_resource(TestResource2("Hello, world!".to_string()));
world.insert_resource(TestResource3);
world.remove_resource::<TestResource3>();

let mut iter = world.iter_resources_mut();

let (info, mut mut_untyped) = iter.next().unwrap();
assert_eq!(info.name(), std::any::type_name::<TestResource>());
// SAFETY: We know that the resource is of type `TestResource`
unsafe {
mut_untyped.as_mut().deref_mut::<TestResource>().0 = 43;
};

let (info, mut mut_untyped) = iter.next().unwrap();
assert_eq!(info.name(), std::any::type_name::<TestResource2>());
// SAFETY: We know that the resource is of type `TestResource2`
unsafe {
mut_untyped.as_mut().deref_mut::<TestResource2>().0 = "Hello, world?".to_string();
};

assert!(iter.next().is_none());
std::mem::drop(iter);

assert_eq!(world.resource::<TestResource>().0, 43);
assert_eq!(
world.resource::<TestResource2>().0,
"Hello, world?".to_string()
);
}

#[test]
fn custom_resource_with_layout() {
static DROP_COUNT: AtomicU32 = AtomicU32::new(0);
Expand Down

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