entity_data 0.2.0

A container for entity component data.
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# entity_data


[![Build Status][build_img]][build_lnk] [![Crates.io][crates_img]][crates_lnk] [![Docs.rs][doc_img]][doc_lnk]

[build_img]: https://github.com/a7292969/entity_data/actions/workflows/build.yml/badge.svg
[build_lnk]: https://github.com/a7292969/entity_data/actions
[crates_img]: https://img.shields.io/crates/v/entity_data.svg
[crates_lnk]: https://crates.io/crates/entity_data
[doc_img]: https://docs.rs/entity_data/badge.svg
[doc_lnk]: https://docs.rs/entity_data

A container for entity component data.

An entity is an opaque identifier for an object.
Each entity can have multiple components associated with it.
Storage is based on [ECS](https://en.wikipedia.org/wiki/Entity_component_system) technique,
but the main purpose is to efficiently store and access
individual components without `Box`ing them.

The approach used in this library is superior to Rust's dynamic dispatch because
components can have their separate fields and components of the
same type are stored in a contiguous vector.

## Example


```rust
use entity_data::EntityStorageLayout;
use entity_data::EntityStorage;

struct Barks {
    bark_sound: String,
}

impl Barks {
    fn bark(&self) {
        println!("{}", self.bark_sound);
    }
}

struct Eats {
    eaten_food: Vec<String>,
}

impl Eats {
    fn eat(&mut self, food: String) {
        self.eaten_food.push(food);
    }
}

struct Dog {
    favorite_food: String,
}

struct Bird {
    weight: f32,
    habitat: String,
}

fn main() {
    let mut layout = EntityStorageLayout::new();
    let type_dog = layout.add_archetype().with::<Dog>().with::<Barks>().with::<Eats>().build();
    let type_bird = layout.add_archetype().with::<Bird>().with::<Eats>().build();

    let mut storage = EntityStorage::new(&layout);

    let super_dog = storage.add_entity(type_dog)
        .with(Dog { favorite_food: "meat".to_string(), })
        .with(Eats { eaten_food: vec![] })
        .with(Barks { bark_sound: "bark.ogg".to_string() })
        .build();

    let hummingbird = storage.add_entity(type_bird)
        .with(Bird { weight: 0.07, habitat: "gardens".to_string() })
        .with(Eats { eaten_food: vec![] })
        .build();
    
    let super_dog_barks = storage.get::<Barks>(&super_dog).unwrap();
    super_dog_barks.bark();

    let super_dog_props = storage.get_mut::<Dog>(&super_dog).unwrap();
    super_dog_props.favorite_food = "beans".to_string();

    let hummingbird_eats = storage.get_mut::<Eats>(&hummingbird).unwrap();
    hummingbird_eats.eat("seeds".to_string());
}
```