flecs_ecs 0.2.2

use crate::z_ignore_test_common::*;

use flecs_ecs::prelude::*;
// Nested prefabs make it possible to reuse an existing prefab inside another
// prefab. An example of where this could be useful is a car with four wheels:
// instead of defining four times what a wheel is a Car prefab can reference an
// existing Wheel prefab.
//
// Nested prefabs can be created by adding a child that is a variant (inherits
// from) another prefab. For more information on variants, see the variants
// example.
//
// Instantiated children from a nested prefab still inherit from the original
// prefab. The reason for this is that an instantiated child is an exact copy
// of the prefab child, and the prefab child only has an IsA relationship to the
// nested prefab.

#[derive(Debug, Component, Clone)]
struct TirePressure {
    value: f32,
}

fn main() {
    let world = World::new();

    // Creates a wheel prefab
    let wheel = world.prefab_named("Wheel");
    wheel.set(TirePressure { value: 32.0 });

    // Create a Car prefab with four wheels. Note how we're using the scope
    // method, which has the same effect as adding the (ChildOf, Car) pair.
    let car = world.prefab_named("Car");
    car.run_in_scope(|| {
        world.prefab_named("FrontLeft").is_a(wheel);

        world.prefab_named("FrontRight").is_a(wheel);

        world.prefab_named("BackLeft").is_a(wheel);

        world.prefab_named("BackRight").is_a(wheel);
    });

    // Create a prefab instance.
    let inst_car = world.entity_named("my_car");
    inst_car.is_a(car);

    // Lookup one of the wheels
    if let Some(inst) = inst_car.try_lookup_recursive("FrontLeft") {
        // The type shows that the child has a private copy of the TirePressure
        // component, and an IsA relationship to the Wheel prefab.
        println!("{:?}", inst.archetype());

        // Get the TirePressure component & print its value
        inst.try_get::<Option<&TirePressure>>(|p| {
            if let Some(p) = p {
                println!("pressure: {}", p.value);
            }
        });
    } else {
        println!("entity lookup failed");
    }

    // Output:
    //  TirePressure, (Identifier,Name), (ChildOf,my_car), (IsA,Wheel)
    //  pressure: 32
}

#[cfg(feature = "flecs_nightly_tests")]
#[test]
fn test() {
    let output_capture = OutputCapture::capture().unwrap();
    main();
    output_capture.test("prefab_nested".to_string());
}