Cache added and removed components

main.lua

@@ -35,11 +35,12 @@ end)
 
 local test_system = System("test_system", {Components.test_comp_1})
 
-local function onEntityAdded(e) -- luacheck: ignore
-    print("Added")
+local function onEntityAdded(pool, e) -- luacheck: ignore
+    local test_comp = e:get(Components.test_comp_1)
+    print(test_comp.x)
 end
 
-local function onEntityRemoved(e) -- luacheck: ignore
+local function onEntityRemoved(pool, e) -- luacheck: ignore
     print("Removed")
 end
 
@@ -64,7 +65,11 @@ end
 local world = World("testWorld")
 
 local entity = Entity()
-entity:give(Components.test_comp_1, 100, 100)
+entity
+:give(Components.test_comp_1, 100, 100)
+:remove(Components.test_comp_1)
+:give(Components.test_comp_1, 200, 100)
+
 
 Worlds.testWorld:addEntity(entity)
 

src/component.lua

@@ -38,7 +38,10 @@ end
 -- @return A new initialized Bag
 function Component:__initialize(...)
    if self.__populate then
-      local bag = setmetatable({}, self)
+      local bag = setmetatable({
+         __baseComponent = self,
+      }, self)
+
       self.__populate(bag, ...)
 
       return bag

src/entity.lua

@@ -13,9 +13,13 @@ function Entity.new()
    local e = setmetatable({
       world = nil,
 
+      __addedComponents   = {},
+      __removedComponents = {},
+      __operations        = {},
+
       __components = {},
 
-      __isDirty    = true,
+      __isDirty    = false,
       __wasAdded   = false,
       __wasRemoved = false,
 
@@ -25,18 +29,30 @@ function Entity.new()
    return e
 end
 
-local function give(e, baseComponent, ...)
-   local component = baseComponent:__initialize(...)
+local function giveOperation(e, component)
+   local baseComponent = component.__baseComponent
 
    e[baseComponent] = component
    e.__components[baseComponent] = component
+end
+
+local function removeOperation(e, baseComponent)
+   e[baseComponent] = nil
+   e.__components[baseComponent] = nil
+end
+
+local function give(e, baseComponent, ...)
+   local component = baseComponent:__initialize(...)
+
+   e.__addedComponents[#e.__addedComponents + 1] = component
+   e.__operations[#e.__operations + 1] = giveOperation
 
    e.__isDirty = true
 end
 
 local function remove(e, baseComponent)
-   e[baseComponent] = nil
-   e.__components[baseComponent] = nil
+   e.__removedComponents[#e.__removedComponents + 1] = baseComponent
+   e.__operations[#e.__operations + 1] = removeOperation
 
    e.__isDirty = true
 end
@@ -92,6 +108,26 @@ function Entity:assemble(assemblage, ...)
    return self
 end
 
+function Entity:flush()
+   local addi, removei = 1, 1
+
+   for i = 1, #self.__operations do
+      local operation = self.__operations[i]
+
+      if (operation == giveOperation) then
+         operation(self, self.__addedComponents[addi])
+         self.__addedComponents[addi] = nil
+         addi = addi + 1
+      elseif (operation == removeOperation) then
+         operation(self, self.__removedComponents[removei])
+         self.__removedComponents[removei] = nil
+         removei = removei + 1
+      end
+
+      self.__operations[i] = nil
+   end
+end
+
 --- Destroys the Entity.
 -- @return self
 function Entity:destroy()

src/world.lua

@@ -75,9 +75,20 @@ function World:flush()
    for i = 1, self.entities.size do
       e = self.entities:get(i)
 
+      if e.__isDirty then
+         e:flush()
+
+         if (not e.__wasAdded) then -- The __wasAdded check below will handle this instead
+            for j = 1, self.systems.size do
+               self.systems:get(j):__evaluate(e)
+            end
+         end
+
+         e.__isDirty = false
+      end
+
       if e.__wasAdded then
          e.__wasAdded = false
-         e.__isDirty = false
 
          for j = 1, self.systems.size do
             self.systems:get(j):__evaluate(e)
@@ -95,14 +106,8 @@ function World:flush()
          end
 
          e.__wasRemoved = false
-      end
 
-      if e.__isDirty then
-         for j = 1, self.systems.size do
-            self.systems:get(j):__evaluate(e)
-         end
-
-         e.__isDirty = false
+         self:onEntityRemoved(e)
       end
    end