object class and box2d

Comments

• zvardin Member

  January 2013 Accepted Answer

  Puck doesn't have any way to access the world variable you set in the scene. One thing you can do is add a variable to your init function to pass the world in, like such:

  self:addChild(Puck.new(100,100,self.world))   function Puck:init(xp,yp,world) -- your code here end

  
  Also, when posting code to the forums, you can wrap it with a tag to make it more readable, see: http://www.giderosmobile.com/DevCenter/index.php/Forum_FAQ#How_can_I_highlight_my_Lua_code_in_the_forum_post.3F

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• ar2rsawseen Maintainer

  January 2013 edited January 2013 Accepted Answer

  For someone who is not the best in programming you are doing quite great
  
  Well in this case world is the property of Scene3 class, and it would make sense to pass that instance to Puck class (because you may want to get some other properties form scene class, not only world). So here's what we can do:

  function Puck:init(level, xp, yp) --self the reference to scene self.level = level   --all your other code goes here   --and when you want to create a body using world instance: local body = self.level.world:createBody{type = b2.DYNAMIC_BODY} --and the rest of your code end

  Now inside Scene3 class, you just create a Puck like this:

  --passing reference to Scene3 which is self self:addChild(Puck.new(self,100,100))

  But there are also other options, you can pass self.world directly, or make world instance global, or have a global object with world instance as property, etc.
  
  P.S ninjajed by @zvardin just don't tell anyone

  http://appcodingeasy.com/Gideros-Mobile

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• peach303 Member

  January 2013 edited January 2013

  It works! Thx a lot!
  
  @ ar2rsawseen: just seen your comment. Thx a for help!
  
  These answers came really fast

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• peach303 Member

  January 2013

  Now im stuck with another problem.

  function Puck:onTouchesBegin(event) if self:hitTestPoint(event.x, event.y) then self.focus = true event:stopPropagation() self.puckArrow:setVisible(true) end end

  attempt to index field 'puckArrow' (a nil value)
  
  It's because puckArrow is a local in Puck:init() right?? Maybe i do hard to understand this. But puckArrow is a child of Puck. Why does it not work. I tried to make puckArrow global:

  local puckArrow   function Puck:init(xp, yp, world) puckArrow = Bitmap.new(Texture.new("puckArrow.png")) -- and so on end

  but same Error Message

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• peach303 Member

  January 2013

  Do i have to pass puckArrow trough with a parameter? Like before the box2d world?

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• zvardin Member

  January 2013

  Ok, having self.puckArrow in your Puck class is fine. In fact, when you change it to local then it cannot be accessed at all outside of the class.
  
  your event handler should like something like this:

  self:addEventListener(Event.TOUCHES_BEGIN, self.onTouchesBegin, self)

  I'm not sure where your event listener is added, but you could add this in the constructor (init function) of your Puck class.

  function Puck:onTouchesBegin(event) if self:hitTestPoint(event.x, event.y) then self.focus = true event:stopPropagation() self.puckArrow:setVisible(true) end end   function Puck:init(xp, yp, world) self.puckArrow = Bitmap.new(Texture.new("puckArrow.png") self:addEventListener(Event.TOUCHES_BEGIN, self.onTouchesBegin, self) --and so on end

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• zvardin Member

  January 2013

  With the way OOP works in Gideros, you can basically think of local variables in your file like a static/constant for that class. So, if you can have more than one Puck, you really want to create the image and store it in self.puckArrow like I show above because the local variable will not have a separate instance for each puck you make.

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• peach303 Member

  January 2013

  Great! Now it works. Thx again for your help.

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