mirror of
https://github.com/bevyengine/bevy
synced 2024-12-22 19:13:08 +00:00
4847f7e3ad
Remove unnecessary calls to `iter()`/`iter_mut()`.
Mainly updates the use of queries in our code, docs, and examples.
```rust
// From
for _ in list.iter() {
for _ in list.iter_mut() {
// To
for _ in &list {
for _ in &mut list {
```
We already enable the pedantic lint [clippy::explicit_iter_loop](https://rust-lang.github.io/rust-clippy/stable/) inside of Bevy. However, this only warns for a few known types from the standard library.
## Note for reviewers
As you can see the additions and deletions are exactly equal.
Maybe give it a quick skim to check I didn't sneak in a crypto miner, but you don't have to torture yourself by reading every line.
I already experienced enough pain making this PR :)
Co-authored-by: devil-ira <justthecooldude@gmail.com>
116 lines
4.4 KiB
Rust
116 lines
4.4 KiB
Rust
use bevy_ecs::prelude::*;
|
|
use rand::Rng;
|
|
use std::ops::Deref;
|
|
|
|
// In this example we will simulate a population of entities. In every tick we will:
|
|
// 1. spawn a new entity with a certain possibility
|
|
// 2. age all entities
|
|
// 3. despawn entities with age > 2
|
|
//
|
|
// To demonstrate change detection, there are some console outputs based on changes in
|
|
// the EntityCounter resource and updated Age components
|
|
fn main() {
|
|
// Create a new empty World to hold our Entities, Components and Resources
|
|
let mut world = World::new();
|
|
|
|
// Add the counter resource to remember how many entities where spawned
|
|
world.insert_resource(EntityCounter { value: 0 });
|
|
|
|
// Create a new Schedule, which defines an execution strategy for Systems
|
|
let mut schedule = Schedule::default();
|
|
// Create a Stage to add to our Schedule. Each Stage in a schedule runs all of its systems
|
|
// before moving on to the next Stage
|
|
let mut update = SystemStage::parallel();
|
|
|
|
// Add systems to the Stage to execute our app logic
|
|
// We can label our systems to force a specific run-order between some of them
|
|
update.add_system(spawn_entities.label(SimulationSystem::Spawn));
|
|
update.add_system(print_counter_when_changed.after(SimulationSystem::Spawn));
|
|
update.add_system(age_all_entities.label(SimulationSystem::Age));
|
|
update.add_system(remove_old_entities.after(SimulationSystem::Age));
|
|
update.add_system(print_changed_entities.after(SimulationSystem::Age));
|
|
// Add the Stage with our systems to the Schedule
|
|
schedule.add_stage("update", update);
|
|
|
|
// Simulate 10 frames in our world
|
|
for iteration in 1..=10 {
|
|
println!("Simulating frame {}/10", iteration);
|
|
schedule.run(&mut world);
|
|
}
|
|
}
|
|
|
|
// This struct will be used as a Resource keeping track of the total amount of spawned entities
|
|
#[derive(Debug)]
|
|
struct EntityCounter {
|
|
pub value: i32,
|
|
}
|
|
|
|
// This struct represents a Component and holds the age in frames of the entity it gets assigned to
|
|
#[derive(Component, Default, Debug)]
|
|
struct Age {
|
|
frames: i32,
|
|
}
|
|
|
|
// System labels to enforce a run order of our systems
|
|
#[derive(SystemLabel, Debug, Clone, PartialEq, Eq, Hash)]
|
|
enum SimulationSystem {
|
|
Spawn,
|
|
Age,
|
|
}
|
|
|
|
// This system randomly spawns a new entity in 60% of all frames
|
|
// The entity will start with an age of 0 frames
|
|
// If an entity gets spawned, we increase the counter in the EntityCounter resource
|
|
fn spawn_entities(mut commands: Commands, mut entity_counter: ResMut<EntityCounter>) {
|
|
if rand::thread_rng().gen_bool(0.6) {
|
|
let entity_id = commands.spawn().insert(Age::default()).id();
|
|
println!(" spawning {:?}", entity_id);
|
|
entity_counter.value += 1;
|
|
}
|
|
}
|
|
|
|
// This system prints out changes in our entity collection
|
|
// For every entity that just got the Age component added we will print that it's the
|
|
// entities first birthday. These entities where spawned in the previous frame.
|
|
// For every entity with a changed Age component we will print the new value.
|
|
// In this example the Age component is changed in every frame, so we don't actually
|
|
// need the `Changed` here, but it is still used for the purpose of demonstration.
|
|
fn print_changed_entities(
|
|
entity_with_added_component: Query<Entity, Added<Age>>,
|
|
entity_with_mutated_component: Query<(Entity, &Age), Changed<Age>>,
|
|
) {
|
|
for entity in &entity_with_added_component {
|
|
println!(" {:?} has it's first birthday!", entity);
|
|
}
|
|
for (entity, value) in &entity_with_mutated_component {
|
|
println!(" {:?} is now {:?} frames old", entity, value);
|
|
}
|
|
}
|
|
|
|
// This system iterates over all entities and increases their age in every frame
|
|
fn age_all_entities(mut entities: Query<&mut Age>) {
|
|
for mut age in &mut entities {
|
|
age.frames += 1;
|
|
}
|
|
}
|
|
|
|
// This system iterates over all entities in every frame and despawns entities older than 2 frames
|
|
fn remove_old_entities(mut commands: Commands, entities: Query<(Entity, &Age)>) {
|
|
for (entity, age) in &entities {
|
|
if age.frames > 2 {
|
|
println!(" despawning {:?} due to age > 2", entity);
|
|
commands.entity(entity).despawn();
|
|
}
|
|
}
|
|
}
|
|
|
|
// This system will print the new counter value everytime it was changed since
|
|
// the last execution of the system.
|
|
fn print_counter_when_changed(entity_counter: Res<EntityCounter>) {
|
|
if entity_counter.is_changed() {
|
|
println!(
|
|
" total number of entities spawned: {}",
|
|
entity_counter.deref().value
|
|
);
|
|
}
|
|
}
|