bevy-resources

name	bevy-resources
description	Reference for Bevy resources — defining, inserting, initializing, reading/writing, and removing global singleton data.
metadata	{"crate":"bevy_ecs","bevy":"0.19"}

Defining a resource

#[derive(Resource)]
struct Score(usize);

Only one per type per World.

Adding resources

// With an instance
app.insert_resource(Score(0));

// With Default or FromWorld
app.init_resource::<Score>();

Dynamic insertion from a system:

commands.insert_resource(Score(0));

Removing resources

commands.remove_resource::<Score>();

Reading and writing

fn read(score: Res<Score>) { }
fn write(mut score: ResMut<Score>) {
  score.0 += 1;
}

Optional resources

Avoid panics when resource might not exist:

fn maybe_score(mut score: Option<ResMut<Score>>) {
  if let Some(mut score) = score.as_deref_mut() {
    score.0 += 1;
  }
}

Prefer init_resource at app definition over dynamic creation to ensure availability.