Module world 

The world: entities, their components, and the scopes they live in.

Components live in UnsafeCells so that a shared &World can reach them, and a borrow ledger written through that same shared reference catches two access paths reaching one value when at least one of them writes. The world is therefore !Send: it stays on the thread that created it, which is where a renderer or any other !Send state lives.

Reading and writing components needs only &World. Structural changes – spawning and despawning – need &mut World. A callback that only has a shared world can queue those changes instead with crate::Commands and apply them later with World::apply.

Every entity lives in a scope, and a scope is another entity: the one the world’s tree says it lives in. The world therefore holds a tree, and the entry points that read or write it are scopes of a scope rather than methods on the world – Scope and ScopeMut. A scope sees its own subtree and nothing beside it; only &World reaches the root.

An entity’s components are fixed when it is spawned; there is no way to add or remove one later. To change the set of components, despawn the entity and spawn a new one.

A borrow conflict is a panic, not a compile error: two claims the ledger cannot share — a shared claim still held while a write asks for the same component, or the same component fetched as &mut twice in one query — report the component’s name and both claim sites, then stop. This is the trade for not doing access analysis. An optional component is optional only about the component being absent: a conflict over one the row does carry panics as well.

Re-exports

use core::any::TypeId; 🔒

use core::cell::Ref; 🔒

use core::cell::RefCell; 🔒

use core::cell::RefMut; 🔒

use std::collections::VecDeque; 🔒

use crate::archetype::Archetype; 🔒

use crate::archetype::Archetypes; 🔒

use crate::borrow::BorrowLedger; 🔒

use crate::borrow::Rows; 🔒

use crate::bundle::Bundle; 🔒

use crate::bundle::BundleComponent; 🔒

use crate::bundle::DynamicBundle; 🔒

use crate::column::AnyColumn; 🔒

use crate::command::Command; 🔒

use crate::entity::Entities; 🔒

use crate::entity::Entity; 🔒

use crate::entity::Location; 🔒

use crate::error::EntityAccessError; 🔒

use crate::hash::TypeIdHashMap; 🔒

use crate::lifecycle::Lifecycle; 🔒

use crate::lifecycle::LifecycleCallback; 🔒

use crate::query::Mode; 🔒

use crate::scope::ScopeTree; 🔒

use crate::view::Scope; 🔒

use crate::view::ScopeMut; 🔒

Structs

World

Entities and their components.

Type Aliases

CommandsGuard 🔒

The exclusive borrow of a world’s command queue.