component.nim

import options, tables
import ../entity

template simpleTableComponent*(Type, name) =
  let table = newTable[Entity, Type]()
  
  proc name*(entity: Entity): Option[Type] =
    try: table[entity].some
    except KeyError: Type.none
  
  proc `name=`*(entity: Entity, value: Type) =
    table[entity] = value
  
  proc `name=`*(entity: Entity, value: Option[Type]) =
    if value.isSome: table[entity] = value.get
    else: table.del(entity)

location.nim

import options, strutils, tables
import component, ../entity

type
  Location* = object
    x*: int
    y*: int

simpleTableComponent(Location, location)

converter toLocation*(value: tuple[x: int, y: int]): Location =
  Location(x: value.x, y: value.y)

proc `$`*(loc: Location): string =
  "($1, $2)" % [$loc.x, $loc.y]

main.nim

import options
import ./entity
import ./components/location

let me = newEntity()

echo $me.location
me.location = (1, 1)
echo $me.location