3 releases

0.1.3 Jul 31, 2023
0.1.2 Jun 30, 2023
0.1.0 Jun 27, 2023

#991 in Procedural macros

21 downloads per month
Used in trecs

Custom license

7KB
111 lines

a tiny entity-component-system library

  • less dependencies

  • fast to build

  • easy to use

Hello World

// a function-system
fn hello_world() {
    println!("Hello World")
}

fn main() {
    // create a world
    let mut world = tecs::World::new();
    world
    // add "hello world" system into world's start_up_systems
    // startup_systems will only run once
    .add_startup_system(hello_world)
    // make the loop run once only
    .run_until(|| true);
}

add components into world

you can use spawn method to add any types that implemented Bundle or Component trait into world

use tecs::tools::Command;

let mut world = tecs::World::new();
world.spawn(12345);
world.spawn("abcde");

you can derive Bundle and Component trait easily

Component is just a tag, it could be implemented for any type

use tecs::bundle::Component;

#[derive(Component)]
struct MyComponent{
    name : String,
}

all of the field of Bundle should implement Component

use tecs::bundle::Bundle;

#[derive(Bundle)]
struct MyBundle{
    inner : MyComponent,
}

Component defaults to the following type implementation

  • usize,u8,u16,u32,u64
  • isize,i8,i16,i32,i64
  • (),bool,&'static str

Bundle defaults to all tuple implementations that contain only types thatComponent trait implemented

such as:

  • (usize,&str)

query components in world

use Query directly

use tecs::world::Query;
use tecs::tool::Command;

let mut world = tecs::World::new();
// add two `Bundle` into world     
world.spawn(12345);
world.spawn((54321,"abcde"));

// create a `Query` to get all i32'a refence
let query = Query::<&i32>::new(&mut world);
for item in query {
    println!("{item}")
}
// this code will print: 
// 12345
// 54321

or use system

use tecs::world::{Query,Commands};
use tecs::tool::Command;

// use command to do spawn
fn do_spawn(mut commands: Commands){
    commands.spawn(12345);
    commands.spawn((54321,"abcde"));
}

// note: you cant use conflict Query in one system, or the program will panic when you add system into world
// a example of conflict Query: Query<&i32> and Query<&mut i32>
fn print_all_i23(mut query : Query<&i32>){
    for item in query {
        println!("{item}")
    }   
}



world.add_startup_system(do_spawn);
world.add_startup_system(print_all_i23);
world.run_until(||true);

Query is a type that receiver two generic

pub struct Query<'a, F: WorldFetch, Q: WorldFilter = ()> {...}

WorldFetch is used to fetch component in world

it could be the (im)mutable reference of Component,or a tuple that contains only WorldFetch

WorldFilter is used to fetch bundle in world

it could be

  • All or All<(Component1,Component1,...)> to filter bundle that contains all of components

  • OneOf or OneOf<(Component1,Component1,...)> to filter bundle that contains at least one of components

  • Not or Not<(Component1,Component1,...)> to filter bundle that doesnot contain any one of components

Example

  • Query<&i32> will query all components that contain i32 component, and give immutable references of i32 in iterator

  • use Query<&mut i32> to let iterator give mutable references of i32 in iterator

  • use Query<&i32,All<&str>> will query all components that contain i32 and &str, and give immutable references of i32 in iterator

  • use Query<&i32,AnyOf<(&str,MyComponent)>> will query all components that contain i32 and one of &str and MyComponent, and give immutable references of i32 in iterator

  • use Query<&i32,All<&str>> will query all components that contain i32 and dont contain &str, and give immutable references of i32 in iterator

Iterator

you can use for to get the result of the query the type of fetch is WorldFetch

for fetch in query {}

you can use for with .into_eiter() method to get the result of the query,and the Entity of result

for e in query.into_eiter() {}

the type of e is EBundle

pub struct EBundle<'a, F: WorldFetch> {...}

you can deref e to get the result of query, use .entity() method to get the Entity of result

Entity could be used to remove the bundle that queried

commands.remove(b.entity());

resources

Resources are stored in the world type by type

use tecs::tools::ResManager;

let mut world = tecs::World::new();
// get resources usize, and init it to 1
world.get_res<usize>().get_or_init(||1);
assert_eq!(*world.get_res<usize>().get().unwrap(),1);

with system

features: System

this feature is really useful

this feature is enabled by default

this feature allow you to run system in world to access resources and components

only function-system supported in this version

all types that implemented SystemParm trait could be the parm of the function-system

follow types impled SystemParm trait

you can find them in tecs::world mod

type usage note
Res to get resources of type T in world cant use same Res in one system
Resources to get any type of resources in world cant use be used with any Res in one system
Query<F,Q> to query components in world cant use conflict query in one system, like Query<&T> and Query<&mut T>
Commands to add and remove bundle into world use spawn_many() method to spawn many bundle with the same type quickly

to run a system,you need to add system into world by using .add_system() method or .add_startup_system() method fist

  • all startup_systems will only run once
  • systems run pre loop

to run systems in world,you can

  • use .startup() method to run all startup_systems

  • use .run_once() method to run all systems once(dont include startup_systems)

  • use .run() method to run all systems many times, this method will not return.

  • use .run_until(f) method to run all systems many times, the loop will be break when f return true;

features: async

this feature is disabled by default

this feature allow you to run async function-system in world

this feature make you can and only can add async function-system into world, reason:

note: upstream crates may add a new impl of trait `std::future::Future` for type `()` in future versions

the '.startup' '.run_once' '.run' '.run_until' methods become asynchronous functions

Dependencies

~310–730KB
~18K SLoC