julia-ecs.jl

using StaticArrays

mutable struct CAcceleration
  a::SVector{2, Float32}
end

mutable struct CPosition
  p::SVector{2, Float32}
end

mutable struct CVelocity
  v::SVector{2, Float32}
end

function SVelocity(entity) 
  if CVelocity ∈ components(entity) && CAcceleration ∈ components(entity)
    entity[CVelocity].v += entity[CAcceleration].a
  end
end

function SPosition(entity) 
  if CPosition ∈ components(entity) && CVelocity ∈ components(entity)
    entity[CPosition].p += entity[CVelocity].v
  end
end

entities = []
components = keys
systems = [SPosition, SVelocity]

const Entity = Dict{DataType, Any}

function pushentity!(components::Pair{DataType, <:Any}...)
  entity = Entity()
  for component ∈ components
    entity[first(component)] = first(component)(last(component))
  end
  push!(entities, entity)
end

pushentity!(CPosition => [0, 0], CVelocity => [1, 3], CAcceleration => [1, 0])
pushentity!(CPosition => [0, 0], CVelocity => [2, 1])

for _ ∈ 0:100, system ∈ systems, entity ∈ entities
  system(entity)
end

for entity ∈ entities
  println(entity)
end