Trait Plugin

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pub trait Plugin:
    Downcast
    + Any
    + Send
    + Sync {
    // Required method
    fn build(&self, app: &mut App);

    // Provided methods
    fn ready(&self, _app: &App) -> bool { ... }
    fn finish(&self, _app: &mut App) { ... }
    fn cleanup(&self, _app: &mut App) { ... }
    fn name(&self) -> &str { ... }
    fn is_unique(&self) -> bool { ... }
}

Expand description

A collection of Bevy app logic and configuration.

Plugins configure an App. When an App registers a plugin, the plugin’s Plugin::build function is run. By default, a plugin can only be added once to an App.

If the plugin may need to be added twice or more, the function is_unique() should be overridden to return false. Plugins are considered duplicate if they have the same name(). The default name() implementation returns the type name, which means generic plugins with different type parameters will not be considered duplicates.

§Lifecycle of a plugin

When adding a plugin to an App:

the app calls Plugin::build immediately, and register the plugin
once the app started, it will wait for all registered Plugin::ready to return true
it will then call all registered Plugin::finish
and call all registered Plugin::cleanup

§Defining a plugin.

Most plugins are simply functions that add configuration to an App.

App::new().add_plugins(my_plugin).run();

// This function implements `Plugin`, along with every other `fn(&mut App)`.
pub fn my_plugin(app: &mut App) {
    app.add_systems(Update, hello_world);
}

For more advanced use cases, the Plugin trait can be implemented manually for a type.

pub struct AccessibilityPlugin {
    pub flicker_damping: bool,
    // ...
}

impl Plugin for AccessibilityPlugin {
    fn build(&self, app: &mut App) {
        if self.flicker_damping {
            app.add_systems(PostUpdate, damp_flickering);
        }
    }
}

Required Methods§

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fn build(&self, app: &mut App)

Configures the App to which this plugin is added.

Provided Methods§

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fn ready(&self, _app: &App) -> bool

Has the plugin finished its setup? This can be useful for plugins that need something asynchronous to happen before they can finish their setup, like the initialization of a renderer. Once the plugin is ready, finish should be called.

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fn finish(&self, _app: &mut App)

Finish adding this plugin to the App, once all plugins registered are ready. This can be useful for plugins that depends on another plugin asynchronous setup, like the renderer.

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fn cleanup(&self, _app: &mut App)

Runs after all plugins are built and finished, but before the app schedule is executed. This can be useful if you have some resource that other plugins need during their build step, but after build you want to remove it and send it to another thread.

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