bevy-state-machines

사용 방법

설치 명령을 복사하고 자신의 에이전트 환경에 설치하기 전에 소스 패키지를 확인하세요.
필요한 도구, 인증 정보, 지원 환경은 원본 문서에서 확인하세요.
입력과 원하는 산출물을 설명하고 출처와 결과를 대조하세요.

npx skills add https://github.com/thedivergentai/game-design-agentic-skills --skill bevy-state-machines

시작 전 확인

설치에는 모델 구독, API 한도, 파일 접근 권한이 포함되지 않습니다.
별점 수와 설치 수는 활동 지표이며 독립적인 품질·보안 검증이 아닙니다.

원본 Skill 문서

원본 저장소의 제목, 예시, 코드, 표, 링크, 이미지를 유지해 표시합니다.

Bevy state machines

When to use

Load this when the app needs a large-scale mode (paused, in a menu, loading) or when one entity needs a small mode flag. Use bevy::state for the first. Use a component for the second. Do not merge them into one Godot-style state graph.

ECS shape

App states. bevy::state: states are app-wide finite state machines. Three types implement States.
Standard states change only by setting the NextState<S> resource.
SubStates also use NextState<S>, and are removed from the World when source states are not in the required state.
ComputedStates derive from other states through a compute method.
Transition schedules. OnEnter<S>, OnExit<S>, and OnTransition<S> run systems on matching transitions. StateTransitionEvent<S> fires when state S changes. Run conditions: in_state<S> and state_changed<S>.
Entity lifetime. DespawnOnEnter<S> and DespawnOnExit<S> despawn entities on those transitions (state_scoped).
Feature. The bevy 0.20.0 crate page includes bevy_state in the default_app collection. The state module was opened; App installation method names were not. Do not invent init_state or similar.
Per-entity mode. Store an enum in a Component and branch in a system (Query from the ECS page). No per-entity state-machine type was opened.

Coming from Godot

Godot idea	Bevy idiom
App mode (menu, pause, play)	A `States` type and `NextState<S>`
Run logic only in one mode	`in_state` or an `OnEnter` / `OnExit` / `OnTransition` schedule
Child mode that exists only inside a parent mode	`SubStates`
Mode derived from other modes	`ComputedStates`
One actor's animation or combat mode	An enum `Component` plus a system. Not `States` unless it is truly app-wide

Scope

Check bevy::state::app for state installation methods on App before writing them.
The module names states, sub-states, and computed-state examples. Check those examples before writing them.
Hierarchical per-entity graphs, transition tables, and animation state machines are yours to build. Check the state docs before assuming a built-in type.

Expert Knowledge Delta

Target: Bevy 0.20+.

Core ECS types: Component, Resource, Query, Commands, Startup, Update, Fixed / FixedMain (bevy::time), .chain(), Plugin, DefaultPlugins, MinimalPlugins. Messages and observers are an ownership slot. See bevy-events-messaging for their APIs. Systems run in parallel unless .chain() orders the ones that conflict.

Who owns state

Piece	Owner	Who may mutate	Schedule
Data on one entity	`Component`	One system via `Query`	`Update` or `FixedMain`
One value for the whole app	`Resource`	One system	`Startup` to insert, then the schedule that reads it
Spawn	`Commands`	The spawning system	`Startup` for the initial world; later schedules for runtime spawn
Order that must not race	`.chain()`	The chained systems only	Same schedule
Plugin boundary	`Plugin`	`build` registers systems and resources	Before the app runs

Borrow rule: two systems that both mutably query the same component must be ordered (.chain()) or split so only one writes. Unrelated systems stay parallel. That is the ECS page rule, not a guess at a system-set API.

Decision

If you need	Do this	Do not
Per-entity data	`Component` + `Query`	A Godot node script
App-wide config or clock	`Resource`	Copy the value onto every entity
Stable simulation step	`FixedMain` and the `Fixed` clock	Tie simulation to raw frame `Update`
Startup spawn	`Commands` in `Startup`	Spawn from a render system
Cross-system notice that is not shared state	Message or observer slot in `bevy-events-messaging`	A new event type invented in this file
An API outside the documented set	Check the official docs first	A made-up crate or API

Load references/ecs-ownership.md for the ownership table.

NEVER

Do not pin /0.20.0/ in docs URLs. WHY: links stay on latest; the 0.20 target is stated once in prose.
Do not mutably query the same component from two unordered systems. WHY: the schedule runs systems in parallel unless .chain() orders them.
Do not invent a physics, navigation, networking, or XR crate here. WHY: this skill only names documented Bevy crates and modules.

No Godot animation-tree or node state-machine types. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.
No invented App state-setup methods. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.
No third-party crates. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

Reference

docs.rs links use the unversioned latest permalink. The library pin on bevy-master stays 0.20.0.

Official Documentation

Migration guides - Unversioned hop index.
bevy crate - bevy_state ships inside the default_app collection.
bevy::state - States, NextState, SubStates, ComputedStates, transition schedules, StateTransitionEvent, in_state, state_changed, DespawnOnEnter, DespawnOnExit.
Quick Start: ECS - Component and Query for a per-entity mode flag.
Examples - Example tree on the latest branch. State examples live in that tree.

Related Skills

Prerequisites

bevy-master - Schedules versus a scene tree.
bevy-data-resources - NextState<S> is a resource. Per-entity modes are components.

Complements

bevy-events-messaging - Messages and observers that are not state transitions.
godot-state-machine-advanced - Equivalent Godot skill. Do not import Godot types.