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    Getting Started - Global Index question

    rdominellirdominelli Member
    edited January 2013 in General questions
    I apologize for the newbie nature of this question, I am coming to LUA and Gideros from objective c and java and I expect that's causing me more grief then helping.

    I am trying to adopt the basic box2d tutorial (http://appcodingeasy.com/Gideros-Mobile/Gideros-Box2D-basics) from appcodingeasy to do the following
    1. Have 2 balls falling
    2. When the balls collide, weld them together and stop movement.

    This tutorial was a great starting point but now that I am trying to expand it I have hit a problem

    Looking at the code, it seems that the main.lua is an derived class from sprite.
    scene = gideros.class(Sprite)
    What seems to be tripping me up is the onBeginContact event does not seem to be firing a class method
    	self.world:addEventListener(Event.BEGIN_CONTACT, onBeginContact)
    So when I attempt to do
    	 	local jd = b2.createWeldJointDef(bodyA, bodyB, bodyA:getPosition(), bodyB:getPosition())
		weldJoint = world.createJoint(jd)
    I receive "attempt to index global 'world' (a nil value)" this is also true if I try to specify self.world.

    So my question is how do I access the world object within onBeginContact if its a member variable of scene.

    Thanks for your help.

    Rich in NY.
    Tagged:
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    Comments

    • zvardinzvardin Member
      You can pass additional information to the event listener by adding a 3rd parameter.

      so you can do:
      local function onBeginContact(world, event)
  local jd = b2.createWeldJointDef(bodyA, bodyB, bodyA:getPosition(), bodyB:getPosition())
  weldJoint = world:createJoint(jd)
end
 
self.world:addEventListener(Event.BEGIN_CONTACT, onBeginContact, self.world)
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    • ar2rsawseenar2rsawseen Maintainer
      edited January 2013
      @rdominelli in your case I'd define onBeginContact method as class method
      function scene:onBeginContact(e)
 ....
end
      and then add event as
      self.world:addEventListener(Event.BEGIN_CONTACT, self.onBeginContact, self)
      thus you will have all properties and method available from same scene class instance including self.world
      http://appcodingeasy.com/Gideros-Mobile
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    • rdominellirdominelli Member
      Thank you this resolved my issues, can you pass multiple params to events. For instance if I want to use a timer event, can I send multiple params to the onTimer function?
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    • ScouserScouser Guru
      edited January 2013
      @rdominelli: The easy way to send multiple parameters would be to add your extra parameters to the event table.
      local event = Event.new("mytimerevent")
event.data1 = "12345"
event.data2 = "abcde"
 
mydispatcher:dispatchEvent(event)
      See here for more.
      Twitter: https://twitter.com/#!/scouser
      Website: http://www.castlegateinteractive.com
      https://play.google.com/store/apps/developer?id=Castlegate+Interactive
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    • rdominellirdominelli Member
      Thank you for this
      +1 -1Share on Facebook
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