Bevy 0.19 — ECS Queries

When to use this skill

• Reading or writing components from a system.
• Filtering by presence (With/Without), alternation (Or), or change detection (Changed/Added).
• Parallelising over a large entity set with par_iter_mut.
• Borrowing a subset of a query via a lens (transmute_lens).
• Compiler error mentioning IterQueryData or SingleEntityQueryData after upgrading to 0.19.

Canonical pattern

use bevy::prelude::*;

#[derive(Component, Default)]
struct Health(f32);