The destruction of the objects are handled by the garbage-collector metamethod.(Does this make sense? This means that an out-of-scope object will stay visible in game until garbage collection.)

The components of the Entity Component System are not pure-data members,but instead derived classes of a specific base class. (For example Renderable for all renderable objects, Transformable for all movable objects.)Because of this it's not a conventional ECS, but more like a OO + ECS, but up to now it works wonders for me.

I am concerned about the use of design patterns, about the ease-of-use of the API, its scalability and error-proneness.

-- All initing must be done herefunction init( instance ) -- the parameter is the engine api    -- Save API into Engine variable for later use    Engine = instance    -- Create separate apis for accessing different parts of engine using the    -- Engine passed to us    -- And make them all global for further use.    -- ECS - Entity component system interaction.    ECS = Engine:CreateECSAPI()    -- Graphics interaction.    Graphics = Engine:CreateGraphicsAPI()    -- Input handling.    Input = Engine:CreateInputAPI()    -- Setup mouse callback    Input:AddMouseCallback( "OnMouse" )    -- Get index of the forward renderable component.    ForwardComponent = ECS:GetComponentIndex( "renderable_forward" )    -- Create text with given text and font size.    Text = Graphics:CreateTextObject( "The quick brown fox is lazy.", 40 )    Text:SetColor( { 1, 1, 1 } )    Text:SetPosition( { 0, 0.5 } )    -- Create a fullscreen rectanlge as background.    Rect = Graphics:CreateRectangle( { 1.0, 1.0 } )    Rect:SetSize( { 2.0, 2.0 } )    Rect:SetPosition( { 0.0, 0.0 } )    -- Entity must be created for anything to be processed by the engine.    -- Processed can mean rendered/updated/simulated/synchronized.    TextEntity = ECS:CreateEntity()    RectEntity = ECS:CreateEntity()    -- To render something in 2D we must add a renderable to its     -- renderable_forward component.    TextEntity:SetComponent( ForwardComponent, Text )    RectEntity:SetComponent( ForwardComponent, Rect )    -- Current time    Time = 0    Clicks = { "next" = 1 }end-- If we click, it places a "Click" text there.function OnMouse( type, x, y )    if type == Input.Button then        local entity = ECS:CreateEntity()        local textobject = Graphics:CreateTextObject( "Click" )        textobject:SetPosition( { x, y } )        entity:SetComponent( ForwardComponent, textobject )        local next = Clicks["next"]        Clicks[next] = { entity, textobject }        Clicks["next"] = next + 1    endend--Called each frame--dt is the time since last update in seconds.--use it for frame-independent movementfunction update( dt )    -- Save current time by storing the time elapsed.    Time = Time + dt    local s = math.sin( Time )    Rect.SetColor( { s, s, s } )end

• \$\begingroup\$The variable scope in lua, by default, is global. Uselocal everywhere you create variables unless global is needed.\$\endgroup\$

  hjpotter92

  – hjpotter92

  2015-03-30 10:44:25 +00:00

  CommentedMar 30, 2015 at 10:44
• \$\begingroup\$@hjpotter92 I see no instance where something is global that shouldn't be(tough some are not used in this small example). Could you pinpoint which one you mean?\$\endgroup\$

  akaltar

  – akaltar

  2015-03-30 12:06:03 +00:00

  CommentedMar 30, 2015 at 12:06
• \$\begingroup\$The very first statement:Engine = instance\$\endgroup\$

  hjpotter92

  – hjpotter92

  2015-03-30 12:20:15 +00:00

  CommentedMar 30, 2015 at 12:20
• \$\begingroup\$@hjpotter92 While it may not be clear, thats the "handle" to the whole API, so if I need to access it anywhere else in my code(like changing the view matrix, or some other global thing), then I will need it, so its global.\$\endgroup\$

  akaltar

  – akaltar

  2015-03-30 12:22:39 +00:00

  CommentedMar 30, 2015 at 12:22

0

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