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World Dispatcher

The system part of a full ECS (Entity-Component-System).

It also contains a World structure, which holds the game data used by systems, as well as the Dispatcher that is used to execute systems in parallel and in an optimised order.

Why would you use this ECS library?

• Compatible with all platforms, including WASM!
• Fast enough on every operation, not just iteration.
• Minimal amount of dependencies.
• Small code size.
• Stable, tested, benchmarked, 100% completed.

Usage

Add the following to you Cargo.toml file:

world_dispatcher = "*"

Use it like so:

use world_dispatcher::*;
fn main() {
    #[derive(Default)]
    pub struct A;

    let mut world = World::default();

    let sys = (|_comps: &A| Ok(())).system();

    let mut dispatch = DispatcherBuilder::new().add_system(sys).build(&mut world);
    dispatch.run_seq(&world).unwrap();
    dispatch.run_seq(&world).unwrap();
    dispatch.run_seq(&world).unwrap();

    assert!(world.get::<A>().is_ok());
}

It is also possible to convert most functions into systems.

There are five requirements for this:

• Take only & and &mut references as arguments
• Return a SystemResult
• Use all & references before all &mut references in the arguments.
• Do not use the same type twice in the arguments.
• All types in the arguments must implement Default. If they don't, use &/&mut Option<YourType> instead.

use world_dispatcher::*;

#[derive(Default)]
pub struct A;
#[derive(Default)]
pub struct B;
#[derive(Default)]
pub struct C;
pub struct D;

fn system_function(_a: &A, _b: &B, _c: &mut C, d: &mut Option<D>) -> SystemResult {
    assert!(d.is_some());
    Ok(())
}

fn main() {
    let mut world = World::default();
    // Will automatically create A, B, C, Option<D>::None inside of world.
    let mut dispatch = DispatcherBuilder::new().add(system_function).build(&mut world);
    // Let's assign a value to D.
    *world.get_mut::<Option<D>>().unwrap() = Some(D);

    dispatch.run_seq(&world).unwrap();
    dispatch.run_seq(&world).unwrap();
    dispatch.run_seq(&world).unwrap();

    assert!(world.get::<Option<D>>().unwrap().is_some());
}

If you need more than 12 system parameters, there is a feature called big_systems which will bump that limit to 22. First compilation time will be around 10 seconds if using it. Following compilations will be instant.

Maintainer Information

• Maintainer: Jojolepro
• Contact: jojolepro [at] jojolepro [dot] com
• Website: jojolepro.com
• Patreon: patreon