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    Scope problem?

    DafbDafb Member
    in General questions
    I am rewriting my code to implement scenemanager. Being just a hobby programmer, I ran in various expected scope problems. But this one really surprised me.

    So my main.lua for now is
    application:setBackgroundColor(0x000000)
 
print("Starting...")
 
--define scenes
sceneManager = SceneManager.new({
    --start scene
    ["start"] = start,    
    ["level1"] = level1,   
    ["gameover"] = GameOver
})
 
 
--add manager to stage
stage:addChild(sceneManager)
 
sceneManager:changeScene("level1")
    My level1.lua starts with this line:
    level1 = gideros.class(Sprite)
    Somewhere, I have a
    function level1:moveRedMotherShip(dt)
    And its moveBlueMotherShip(dt) equivalent.
    Finally, here is my onEnterFrame function:
    function level1:onEnterFrame(e) 
 
	local dt = e.deltaTime
 
	local numSprite = stage:getNumChildren()
 
	level1:moveRedMotherShip(dt) -- move red ship
	level1:moveBlueMotherShip(dt)
end
    Everything works here. What does not work is when I change
    local numSprite = stage:getNumChildren()
    into
    local numSprite = level1:getNumChildren()
    It spits "index '__userdata' cannot be found"

    Yet,
    level1:moveBlueMotherShip(dt)
    works.
    Why the latter works and not level1:getNumSprite() ? I thought that "level1" being a sprite could call any sprite method. Please enlight me. There is something here I need to understand.

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    Comments

    • MoKaLuxMoKaLux Member
      edited July 2020
      Dafb said:

      level1 = gideros.class(Sprite)
      change it to Core.class(Sprite), it's better.
      Dafb said:

      local numSprite = stage:getNumChildren()
      into
      You need to call:
      local numSprite = self:getNumChildren()
      Dafb said:

      Why the latter works and not level1:getNumSprite() ? I thought that "level1" being a sprite could call any sprite method. Please enlight me. There is something here I need to understand.

      I can't really explain why :o but I think level1 is a class and self is a sprite.

      Likes: hgy29

      my growING GIDEROS github repositories: https://github.com/mokalux?tab=repositories
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    • rrraptorrrraptor Member
      edited July 2020
      Dafb said:

      Why the latter works and not level1:getNumSprite() ? I thought that "level1" being a sprite could call any sprite method. Please enlight me. There is something here I need to understand.

      MoKaLux said:

      I can't really explain why :o but I think level1 is a class and self is a sprite.

      "level1" is a class. And "self" refers to object instance. In your case instance is created by sceneManger.

      @Dafb
      You can read about "self" here: http://www.lua.org/pil/16.html

      Also "level1:getNumSprite()" can be used as "level1.getNumSprite(self)"

      Likes: MoKaLux

      SuperShape | Nice blured shapes with shadows | Simple button pad | Simple layer class | Simple UI library | 2D camera lib | Color picker | FPS graph | Dear ImGui | cute_c2
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    • DafbDafb Member
      Thanks to you guys, I fixed the problem.

      I believe the main issue was I forgot to add

      require ("scenemanager")

      in main.lua.

      Silly stuff! I also use now as advised

      Core.class instead of gideros.class

      Everything works now :) and I will read the provided link.

      Thank you again.



      Likes: MoKaLux

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