From c750ea119fff3e2ec629aff1fd7cf527c97c0430 Mon Sep 17 00:00:00 2001
From: Justin van der Leij <justinvanderleij@gmail.com>
Date: Fri, 16 Feb 2018 15:03:07 +0100
Subject: [PATCH] Made systems classes instead of singletons

---
 fluid/system.lua | 44 +++++++++++++++++++++++++++++---------------
 main.lua         | 29 ++++++++++++++++++-----------
 2 files changed, 47 insertions(+), 26 deletions(-)

diff --git a/fluid/system.lua b/fluid/system.lua
index 3e91746..fee95ea 100644
--- a/fluid/system.lua
+++ b/fluid/system.lua
@@ -4,25 +4,39 @@ local Component = require(PATH..".component")
 local Pool      = require(PATH..".pool")
 
 local System = {}
-System.__index = System
+System.mt    = {
+   __index = System,
+   __call  = function(systemProto, ...)
+      local system = setmetatable({
+         __all   = {},
+         __pools = {},
+      }, systemProto)
+
+      for _, filter in pairs(systemProto.__filter) do
+         local pool = system:__buildPool(filter)
+         if not system[pool.name] then
+            system[pool.name]                   = pool
+            system.__pools[#system.__pools + 1] = pool
+         else
+            error("Pool with name '"..pool.name.."' already exists.")
+         end
+      end
+
+      system:init(...)
+      return system
+   end,
+}
 
 function System.new(...)
-   local system = setmetatable({
-      __all   = {},
-      __pools = {},
-   }, System)
+   local systemProto = setmetatable({
+      __filter = {...},
+   }, System.mt)
+   systemProto.__index = systemProto
 
-   for _, filter in pairs({...}) do
-      local pool = system:__buildPool(filter)
-      if not system[pool.name] then
-         system[pool.name]                 = pool
-         system.__pools[#system.__pools + 1] = pool
-      else
-         error("Pool with name '"..pool.name.."' already exists.")
-      end
-   end
+   return systemProto
+end
 
-   return system
+function System:init(...)
 end
 
 function System:__buildPool(pool)
diff --git a/main.lua b/main.lua
index b2d0441..23151aa 100644
--- a/main.lua
+++ b/main.lua
@@ -31,8 +31,9 @@ end)
 
 local RectangleRenderer = System({Position, Rectangle})
 function RectangleRenderer:draw()
+   local e
    for i = 1, self.pool.size do
-      local e = self.pool:get(i)
+      e = self.pool:get(i)
 
       local position  = e:get(Position)
       local rectangle = e:get(Rectangle)
@@ -49,8 +50,9 @@ end
 
 local CircleRenderer = System({Position, Circle})
 function CircleRenderer:draw()
+   local e
    for i = 1, self.pool.size do
-      local e = self.pool:get(i)
+      e = self.pool:get(i)
 
       local position = e:get(Position)
       local circle   = e:get(Circle)
@@ -66,13 +68,16 @@ function CircleRenderer:draw()
 end
 
 local RandomRemover = System({})
-RandomRemover.time = 0
+
+function RandomRemover:init()
+   self.time = 0
+end
 
 function RandomRemover:update(dt)
-   RandomRemover.time = RandomRemover.time + dt
+   self.time = self.time + dt
 
-   if RandomRemover.time >= 0.125 then
-      RandomRemover.time = 0
+   if self.time >= 0.5 then
+      self.time = 0
 
       if self.pool.size > 0 then
          local i = love.math.random(1, self.pool.size)
@@ -80,13 +85,15 @@ function RandomRemover:update(dt)
          Game:removeEntity(self.pool.objects[i])
       end
    end
+
+   love.window.setTitle(love.timer.getFPS())
 end
 
-Game:addSystem(RandomRemover, "update")
-Game:addSystem(RectangleRenderer, "draw")
-Game:addSystem(CircleRenderer, "draw")
+Game:addSystem(RandomRemover(),     "update")
+Game:addSystem(RectangleRenderer(), "draw")
+Game:addSystem(CircleRenderer(),    "draw")
 
-for i = 1, 50 do
+for i = 1, 100 do
    local e = Entity()
    e:give(Position, love.math.random(0, 700), love.math.random(0, 700))
    e:give(Rectangle, love.math.random(5, 20), love.math.random(5, 20))
@@ -98,7 +105,7 @@ for i = 1, 50 do
    Game:addEntity(e)
 end
 
-for i = 1, 50 do
+for i = 1, 100 do
    local e = Entity()
    e:give(Position, love.math.random(0, 700), love.math.random(0, 700))
    e:give(Circle, love.math.random(5, 20))