992681b59b
*This PR description is an edited copy of #5007, written by @alice-i-cecile.* # Objective Follow-up to https://github.com/bevyengine/bevy/pull/2254. The `Resource` trait currently has a blanket implementation for all types that meet its bounds. While ergonomic, this results in several drawbacks: * it is possible to make confusing, silent mistakes such as inserting a function pointer (Foo) rather than a value (Foo::Bar) as a resource * it is challenging to discover if a type is intended to be used as a resource * we cannot later add customization options (see the [RFC](https://github.com/bevyengine/rfcs/blob/main/rfcs/27-derive-component.md) for the equivalent choice for Component). * dependencies can use the same Rust type as a resource in invisibly conflicting ways * raw Rust types used as resources cannot preserve privacy appropriately, as anyone able to access that type can read and write to internal values * we cannot capture a definitive list of possible resources to display to users in an editor ## Notes to reviewers * Review this commit-by-commit; there's effectively no back-tracking and there's a lot of churn in some of these commits. *ira: My commits are not as well organized :')* * I've relaxed the bound on Local to Send + Sync + 'static: I don't think these concerns apply there, so this can keep things simple. Storing e.g. a u32 in a Local is fine, because there's a variable name attached explaining what it does. * I think this is a bad place for the Resource trait to live, but I've left it in place to make reviewing easier. IMO that's best tackled with https://github.com/bevyengine/bevy/issues/4981. ## Changelog `Resource` is no longer automatically implemented for all matching types. Instead, use the new `#[derive(Resource)]` macro. ## Migration Guide Add `#[derive(Resource)]` to all types you are using as a resource. If you are using a third party type as a resource, wrap it in a tuple struct to bypass orphan rules. Consider deriving `Deref` and `DerefMut` to improve ergonomics. `ClearColor` no longer implements `Component`. Using `ClearColor` as a component in 0.8 did nothing. Use the `ClearColorConfig` in the `Camera3d` and `Camera2d` components instead. Co-authored-by: Alice <alice.i.cecile@gmail.com> Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: devil-ira <justthecooldude@gmail.com> Co-authored-by: Carter Anderson <mcanders1@gmail.com>
45 lines
1.2 KiB
Rust
45 lines
1.2 KiB
Rust
use bevy_ecs::prelude::*;
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use rand::Rng;
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use std::ops::Deref;
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// In this example we add a counter resource and increase it's value in one system,
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// while a different system prints the current count to the console.
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fn main() {
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// Create a world
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let mut world = World::new();
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// Add the counter resource
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world.insert_resource(Counter { value: 0 });
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// Create a schedule and a stage
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let mut schedule = Schedule::default();
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let mut update = SystemStage::parallel();
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// Add systems to increase the counter and to print out the current value
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update.add_system(increase_counter);
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update.add_system(print_counter.after(increase_counter));
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schedule.add_stage("update", update);
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for iteration in 1..=10 {
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println!("Simulating frame {}/10", iteration);
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schedule.run(&mut world);
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}
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}
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// Counter resource to be increased and read by systems
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#[derive(Debug, Resource)]
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struct Counter {
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pub value: i32,
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}
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fn increase_counter(mut counter: ResMut<Counter>) {
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if rand::thread_rng().gen_bool(0.5) {
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counter.value += 1;
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println!(" Increased counter value");
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}
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}
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fn print_counter(counter: Res<Counter>) {
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println!(" {:?}", counter.deref());
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}
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