Document part of bevy_ecs::Commands (#976)

Document part of bevy_ecs::Commands

crates/bevy_ecs/src/core/bundle.rs

@@ -22,6 +22,8 @@ use std::{
 };
 
 /// A dynamically typed collection of components
+///
+/// See [Bundle]
 pub trait DynamicBundle {
     /// Invoke a callback on the fields' type IDs, sorted by descending alignment then id
     #[doc(hidden)]
@@ -38,6 +40,8 @@ pub trait DynamicBundle {
 }
 
 /// A statically typed collection of components
+///
+/// See [DynamicBundle]
 pub trait Bundle: DynamicBundle {
     #[doc(hidden)]
     fn with_static_ids<T>(f: impl FnOnce(&[TypeId]) -> T) -> T;

crates/bevy_ecs/src/core/world.rs

@@ -76,16 +76,16 @@ impl World {
     /// let a = world.spawn((123, "abc"));
     /// let b = world.spawn((456, true));
     /// ```
-    pub fn spawn(&mut self, components: impl DynamicBundle) -> Entity {
+    pub fn spawn(&mut self, bundle: impl DynamicBundle) -> Entity {
         // Ensure all entity allocations are accounted for so `self.entities` can realloc if
         // necessary
         self.flush();
 
         let entity = self.entities.alloc();
-        let archetype_id = components.with_ids(|ids| {
+        let archetype_id = bundle.with_ids(|ids| {
             self.index.get(ids).copied().unwrap_or_else(|| {
                 let x = self.archetypes.len() as u32;
-                self.archetypes.push(Archetype::new(components.type_info()));
+                self.archetypes.push(Archetype::new(bundle.type_info()));
                 self.index.insert(ids.to_vec(), x);
                 self.archetype_generation += 1;
                 x
@@ -95,7 +95,7 @@ impl World {
         let archetype = &mut self.archetypes[archetype_id as usize];
         unsafe {
             let index = archetype.allocate(entity);
-            components.put(|ptr, ty, size| {
+            bundle.put(|ptr, ty, size| {
                 archetype.put_dynamic(ptr, ty, size, index, ComponentFlags::ADDED);
                 true
             });
@@ -566,7 +566,7 @@ impl World {
     pub fn insert(
         &mut self,
         entity: Entity,
-        components: impl DynamicBundle,
+        bundle: impl DynamicBundle,
     ) -> Result<(), NoSuchEntity> {
         use std::collections::hash_map::Entry;
 
@@ -576,7 +576,7 @@ impl World {
             // Assemble Vec<TypeInfo> for the final entity
             let arch = &mut self.archetypes[loc.archetype as usize];
             let mut info = arch.types().to_vec();
-            for ty in components.type_info() {
+            for ty in bundle.type_info() {
                 if let Some(ptr) = arch.get_dynamic(ty.id(), ty.layout().size(), loc.index) {
                     ty.drop(ptr.as_ptr());
                 } else {
@@ -601,7 +601,7 @@ impl World {
             if target == loc.archetype {
                 // Update components in the current archetype
                 let arch = &mut self.archetypes[loc.archetype as usize];
-                components.put(|ptr, ty, size| {
+                bundle.put(|ptr, ty, size| {
                     arch.put_dynamic(ptr, ty, size, loc.index, ComponentFlags::MUTATED);
                     true
                 });
@@ -625,7 +625,7 @@ impl World {
                 self.entities.get_mut(moved).unwrap().index = old_index;
             }
 
-            components.put(|ptr, ty, size| {
+            bundle.put(|ptr, ty, size| {
                 let had_component = source_arch.has_dynamic(ty);
                 let flags = if had_component {
                     ComponentFlags::MUTATED

crates/bevy_ecs/src/system/commands.rs

@@ -16,7 +16,7 @@ pub(crate) struct Spawn<T>
 where
     T: DynamicBundle + Send + Sync + 'static,
 {
-    components: T,
+    bundle: T,
 }
 
 impl<T> Command for Spawn<T>
@@ -24,7 +24,7 @@ where
     T: DynamicBundle + Send + Sync + 'static,
 {
     fn write(self: Box<Self>, world: &mut World, _resources: &mut Resources) {
-        world.spawn(self.components);
+        world.spawn(self.bundle);
     }
 }
 
@@ -33,7 +33,7 @@ where
     I: IntoIterator,
     I::Item: Bundle,
 {
-    components_iter: I,
+    bundles_iter: I,
 }
 
 impl<I> Command for SpawnBatch<I>
@@ -42,7 +42,7 @@ where
     I::Item: Bundle,
 {
     fn write(self: Box<Self>, world: &mut World, _resources: &mut Resources) {
-        world.spawn_batch(self.components_iter);
+        world.spawn_batch(self.bundles_iter);
     }
 }
 
@@ -64,7 +64,7 @@ where
     T: DynamicBundle + Send + Sync + 'static,
 {
     entity: Entity,
-    components: T,
+    bundle: T,
 }
 
 impl<T> Command for Insert<T>
@@ -72,7 +72,7 @@ where
     T: DynamicBundle + Send + Sync + 'static,
 {
     fn write(self: Box<Self>, world: &mut World, _resources: &mut Resources) {
-        world.insert(self.entity, self.components).unwrap();
+        world.insert(self.entity, self.bundle).unwrap();
     }
 }
 
@@ -181,6 +181,7 @@ impl<T: Resource> Command for InsertLocalResource<T> {
     }
 }
 
+/// A list of commands that will be run to populate a `World` and `Resources`.
 #[derive(Default)]
 pub struct Commands {
     commands: Vec<Box<dyn Command>>,
@@ -189,38 +190,78 @@ pub struct Commands {
 }
 
 impl Commands {
-    pub fn spawn(&mut self, components: impl DynamicBundle + Send + Sync + 'static) -> &mut Self {
+    /// Creates a new entity with the components contained in `bundle`.
+    ///
+    /// Note that `bundle` is a [DynamicBundle], which is a collection of components. [DynamicBundle] is automatically implemented for tuples of components. You can also create your own bundle types by deriving [`derive@Bundle`]. If you would like to spawn an entity with a single component, consider wrapping the component in a tuple (which [DynamicBundle] is implemented for).
+    ///
+    /// See [`Self::set_current_entity`], [`Self::insert`].
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use bevy_ecs::prelude::*;
+    ///
+    /// struct Component1;
+    /// struct Component2;
+    ///
+    /// #[derive(Bundle)]
+    /// struct ExampleBundle {
+    ///     a: Component1,
+    ///     b: Component2,
+    /// }
+    ///
+    /// fn example_system(mut commands: Commands) {
+    ///     // Create a new entity with a component bundle.
+    ///     commands.spawn(ExampleBundle {
+    ///         a: Component1,
+    ///         b: Component2,
+    ///     });
+    ///
+    ///     // Create a new entity with a single component.
+    ///     commands.spawn((Component1,));
+    ///     // Create a new entity with two components.
+    ///     commands.spawn((Component1, Component2));
+    /// }
+    /// ```
+    pub fn spawn(&mut self, bundle: impl DynamicBundle + Send + Sync + 'static) -> &mut Self {
         let entity = self
             .entity_reserver
             .as_ref()
             .expect("Entity reserver has not been set.")
             .reserve_entity();
-        self.current_entity = Some(entity);
+        self.set_current_entity(entity);
-        self.commands.push(Box::new(Insert { entity, components }));
+        self.insert(entity, bundle);
         self
     }
 
-    pub fn spawn_batch<I>(&mut self, components_iter: I) -> &mut Self
+    /// Equivalent to iterating `bundles_iter` and calling [`Self::spawn`] on each bundle, but slightly more performant.
+    pub fn spawn_batch<I>(&mut self, bundles_iter: I) -> &mut Self
     where
         I: IntoIterator + Send + Sync + 'static,
         I::Item: Bundle,
     {
-        self.add_command(SpawnBatch { components_iter })
+        self.add_command(SpawnBatch { bundles_iter })
     }
 
-    /// Despawns only the specified entity, ignoring any other consideration.
+    /// Despawns only the specified entity, not including its children.
     pub fn despawn(&mut self, entity: Entity) -> &mut Self {
         self.add_command(Despawn { entity })
     }
 
+    /// Inserts a bundle of components into `entity`.
+    ///
+    /// See [`World::insert`].
     pub fn insert(
         &mut self,
         entity: Entity,
-        components: impl DynamicBundle + Send + Sync + 'static,
+        bundle: impl DynamicBundle + Send + Sync + 'static,
     ) -> &mut Self {
-        self.add_command(Insert { entity, components })
+        self.add_command(Insert { entity, bundle })
     }
 
+    /// Inserts a single component into `entity`.
+    ///
+    /// See [`World::insert_one`].
     pub fn insert_one(&mut self, entity: Entity, component: impl Component) -> &mut Self {
         self.add_command(InsertOne { entity, component })
     }
@@ -229,6 +270,9 @@ impl Commands {
         self.add_command(InsertResource { resource })
     }
 
+    /// Insert a resource that is local to a specific system.
+    ///
+    /// See [`crate::System::id`].
     pub fn insert_local_resource<T: Resource>(
         &mut self,
         system_id: SystemId,
@@ -240,6 +284,7 @@ impl Commands {
         })
     }
 
+    /// See [`World::remove_one`].
     pub fn remove_one<T>(&mut self, entity: Entity) -> &mut Self
     where
         T: Component,
@@ -250,6 +295,7 @@ impl Commands {
         })
     }
 
+    /// See [`World::remove`].
     pub fn remove<T>(&mut self, entity: Entity) -> &mut Self
     where
         T: Bundle + Send + Sync + 'static,
@@ -260,18 +306,54 @@ impl Commands {
         })
     }
 
-    pub fn with_bundle(
+    /// Adds a bundle of components to the current entity.
-        &mut self,
+    ///
-        components: impl DynamicBundle + Send + Sync + 'static,
+    /// See [`Self::with`], [`Self::current_entity`].
-    ) -> &mut Self {
+    pub fn with_bundle(&mut self, bundle: impl DynamicBundle + Send + Sync + 'static) -> &mut Self {
-        let current_entity =  self.current_entity.expect("Cannot add components because the 'current entity' is not set. You should spawn an entity first.");
+        let current_entity =  self.current_entity.expect("Cannot add bundle because the 'current entity' is not set. You should spawn an entity first.");
         self.commands.push(Box::new(Insert {
             entity: current_entity,
-            components,
+            bundle,
         }));
         self
     }
 
+    /// Adds a single component to the current entity.
+    ///
+    /// See [`Self::with_bundle`], [`Self::current_entity`].
+    ///
+    /// # Warning
+    ///
+    /// It's possible to call this with a bundle, but this is likely not intended and [`Self::with_bundle`] should be used instead. If `with` is called with a bundle, the bundle itself will be added as a component instead of the bundles' inner components each being added.
+    ///
+    /// # Example
+    ///
+    /// `with` can be chained with [`Self::spawn`].
+    ///
+    /// ```
+    /// use bevy_ecs::prelude::*;
+    ///
+    /// struct Component1;
+    /// struct Component2;
+    ///
+    /// fn example_system(mut commands: Commands) {
+    ///     // Create a new entity with a `Component1` and `Component2`.
+    ///     commands.spawn((Component1,)).with(Component2);
+    ///
+    ///     // Psst! These are also equivalent to the line above!
+    ///     commands.spawn((Component1, Component2));
+    ///     commands.spawn(()).with(Component1).with(Component2);
+    ///     #[derive(Bundle)]
+    ///     struct ExampleBundle {
+    ///         a: Component1,
+    ///         b: Component2,
+    ///     }
+    ///     commands.spawn(()).with_bundle(ExampleBundle {
+    ///         a: Component1,
+    ///         b: Component2,
+    ///     });
+    /// }
+    /// ```
     pub fn with(&mut self, component: impl Component) -> &mut Self {
         let current_entity =  self.current_entity.expect("Cannot add component because the 'current entity' is not set. You should spawn an entity first.");
         self.commands.push(Box::new(InsertOne {
@@ -281,22 +363,26 @@ impl Commands {
         self
     }
 
+    /// Adds a command directly to the command list. Prefer this to [`Self::add_command_boxed`] if the type of `command` is statically known.
     pub fn add_command<C: Command + 'static>(&mut self, command: C) -> &mut Self {
         self.commands.push(Box::new(command));
         self
     }
 
+    /// See [`Self::add_command`].
     pub fn add_command_boxed(&mut self, command: Box<dyn Command>) -> &mut Self {
         self.commands.push(command);
         self
     }
 
+    /// Runs all the stored commands on `world` and `resources`. The command buffer is emptied as a part of this call.
     pub fn apply(&mut self, world: &mut World, resources: &mut Resources) {
         for command in self.commands.drain(..) {
             command.write(world, resources);
         }
     }
 
+    /// Returns the current entity, set by [`Self::spawn`] or with [`Self::set_current_entity`].
     pub fn current_entity(&self) -> Option<Entity> {
         self.current_entity
     }