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>
49 lines
1.5 KiB
Rust
49 lines
1.5 KiB
Rust
//! Demonstrates the creation and registration of a custom plugin.
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//!
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//! Plugins are the foundation of Bevy. They are scoped sets of components, resources, and systems
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//! that provide a specific piece of functionality (generally the smaller the scope, the better).
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//! This example illustrates how to create a simple plugin that prints out a message.
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use bevy::{prelude::*, utils::Duration};
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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// plugins are registered as part of the "app building" process
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.add_plugin(PrintMessagePlugin {
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wait_duration: Duration::from_secs(1),
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message: "This is an example plugin".to_string(),
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})
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.run();
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}
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// This "print message plugin" prints a `message` every `wait_duration`
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pub struct PrintMessagePlugin {
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// Put your plugin configuration here
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wait_duration: Duration,
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message: String,
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}
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impl Plugin for PrintMessagePlugin {
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// this is where we set up our plugin
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fn build(&self, app: &mut App) {
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let state = PrintMessageState {
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message: self.message.clone(),
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timer: Timer::new(self.wait_duration, true),
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};
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app.insert_resource(state).add_system(print_message_system);
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}
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}
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#[derive(Resource)]
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struct PrintMessageState {
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message: String,
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timer: Timer,
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}
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fn print_message_system(mut state: ResMut<PrintMessageState>, time: Res<Time>) {
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if state.timer.tick(time.delta()).finished() {
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info!("{}", state.message);
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}
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}
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