MothECS: Simple Entity Component System in Swift 📦

MothECS is a simple entity component system written in Swift. It supports the following features:

Use bitmask to manage relationship between entities and components
Support view operation with optional excepted type
Reuse destroyed entity in next creation

Future Development:

Get entity ID from a component
Support more components (currently it supports 32)
Use sparse array

Moth in MothECS - It refers to new players in Sky. Explanation is here!

🔧 Install

You package file would be like:

let package = Package(
    name: "YourPackageName",
    
    dependencies: [
        .package(url: "https://github.com/forkercat/MothECS.git", .branch("main")),
    ],
    
    targets: [
        // For Swift 5.5, use .executableTarget
        .target(
            name: "YourPackageName",
            dependencies: [
                .product(name: "MothECS", package: "MothECS")
            ]),
    ]
)

😆 Usage

Import & Initialize

import MothECS

let moth = Moth()
moth.log()  // use this for showing bitmasks

Define Your Own Component Classes

class TagComponent: MothComponent {
    required init() { }
}

class TransformComponent: MothComponent {
    required init() { }
}

class LightComponent: MothComponent {
    required init() { }
}

Initialize & Create Entity

let e0: MothEntityID = moth.createEntity()
let e1: MothEntityID = moth.createEntity()
let e2: MothEntityID = moth.createEntity()
let e4: MothEntityID = moth.createEntity()
assert(e0 != .invalid)
_ = moth.entityIDs  // return all valid entity IDs

Create & Assign Comonent

moth.createComponent(TagComponent.self, to: e0)
moth.createComponent(TransformComponent.self, to: e0)
moth.createComponent(LightComponent.self, to: e0)   // e0: [Tag, Transform, Light]

moth.assignComponent(TagComponent(), to: e1)
moth.assignComponent(TransformComponent(), to: e1)  // e1: [Tag, Transform]
moth.assignComponent(LightComponent(), to: e2)
moth.assignComponent(TagComponent(), to: e2)        // e2: [Tag, Light]

Remove Entity & Component

moth.removeAllComponents(from: e4)                  // e4: []
moth.removeEntity(entityID: e4)                     // e4 is not invalid, its ID will be reused in next createEntity()
moth.removeComponent(TagComponent.self, from: e2)   // e2: [Light]

Get & Has Component

if moth.hasComponent(LightComponent.self, in: e2) {
    _ = moth.getComponent(LightComponent.self, from: e2)  // put getComponent() inside hasComponent()
}

View Operation

let v1 = moth.view(TagComponent.self, TransformComponent.self, LightComponent.self)
let v2 = moth.view(TagComponent.self, TransformComponent.self)
let v3 = moth.view(TagComponent.self, TransformComponent.self, excepts: LightComponent.self)

// v1: [e0]
// v2: [e0, e1]
// v2: [e1]

🙏 Reference

How to make a simple entity-component-system in C++ by David Colson
fireblade-engine/ecs by @ctreffs

MothECS

main