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//! Shows how anonymous functions / closures can be used as systems.
use bevy::{log::LogPlugin, prelude::*};
fn main() {
// create a simple closure.
let simple_closure = || {
// this is a closure that does nothing.
info!("Hello from a simple closure!");
};
// create a closure, with an 'input' value.
let complex_closure = |mut value: String| {
move || {
info!("Hello from a complex closure! {:?}", value);
// we can modify the value inside the closure. this will be saved between calls.
value = format!("{value} - updated");
// you could also use an outside variable like presented in the inlined closures
// info!("outside_variable! {:?}", outside_variable);
}
};
let outside_variable = "bar".to_string();
App::new()
.add_plugins(LogPlugin::default())
// we can use a closure as a system
.add_systems(Update, simple_closure)
// or we can use a more complex closure, and pass an argument to initialize a Local variable.
.add_systems(Update, complex_closure("foo".into()))
// we can also inline a closure
.add_systems(Update, || {
info!("Hello from an inlined closure!");
})
// or use variables outside a closure
.add_systems(Update, move || {
info!(
"Hello from an inlined closure that captured the 'outside_variable'! {:?}",
outside_variable
);
// you can use outside_variable, or any other variables inside this closure.
// their states will be saved.
})
.run();
}