Need help calling a function inside an object from another function

I need to be able to trigger a function that quietly waits inside an object build function.

A hypothetical example:

local xSpacing = 0
 
function buildBoxes()
  local box = {}
  local i
 
  for i = 1,4 do
     box[i] = display.newRect(20,20,20,20)
     box[i].isVisible = false
 
     local function wakeupThisBox()     -- PROBLEM LINKING FUNCTION TO OBJECT
       box[i].x = xSpacing
       box[i].isVisible = true
     end
  end
end
 
buildBoxes()
box[1].isVisible=true
 
function wakeUpBoxes()
  local n
  for n = 2,4 do
     xSpacing = xSpacing + 25
     box[n]:wakeupThisBox()     -- PROBLEM TRIGGERING THE OBJECT'S INTERNAL FUNCTION
  end
end
 
box[1]:addEventListener("tap",wakeUpBoxes)

both box and wakeupthisbox are local to the function. they wont be visible outside the function

this is how i'd do it

local xSpacing = 0
 
local box={} -- accessible throughout file now
 
local function makeBox() -- let's give each box it's own constructor
  
  local someBox = display.newRect(0,0,20,20)
  someBox.isVisible=false
  someBox:setReferencePoint(display.TopLeftReferencePoint)
 
  function someBox:wakeupThisBox() -- self is inherently passed as a parameter
       self.x = xSpacing
       self.isVisible = true
  end
 
  -- we've built the box locally, now send it back
  return(someBox) 
  
end
 
local function buildBoxes()
 
  local i
 
  for i = 1,4 do
 
     -- call the constructor, 
     -- and stick the result in our array
     box[i] = makeBox() 
 
  end
 
end
 
local function wakeUpBoxes()
  local n
  for n = 2,4 do
     xSpacing = xSpacing + 25
     box[n]:wakeupThisBox()  
  end
end
 
buildBoxes()
box[1].isVisible=true
box[1]:addEventListener("tap",wakeUpBoxes)

sorry for the tangent, but just want to respond to your last comment

well actually i'd have a box module with a metatable (since currently you're creating duplicates of a function for every box, which is a waste of memory), but let's save that for later

"Waste" is a relative term, because it seems to be a tradeoff between speed and memory:
http://developer.anscamobile.com/forum/2011/01/21/oop-game-classes-objects-inheritance-methods-properties

But as I said "it seems." I'm not sure, do you know anything about this matter beyond what was addressed in that thread? I probably wouldn't start using metatables anyway because you can't set the metatable on a display object, but it'd be good to understand the specifics:
http://developer.anscamobile.com/content/display-objects#Display_Objects_vs._Tables:_A_Technical_Discussion

well it depends on how you construct your object. I have a "class" that wraps the display object so the actual display object is reference by eg myInstance.sprite. that way my object isn't intrinsically linked to a loaded image and therefore it is easier to change it's graphic when required

thanks JMP!!!

I used your sample to help me rebuild my function (not the box function above but my real game function) and it works like a champ!!!

It seems that breaking out the build functions from the table array and then returning that object to the table was the key element I was missing. (I actually had the table out of the function in my real life code and not inside per my example.)

Now I am able to RESET my game assets freely to a default state without destroying them and rebuilding them (laggy solution)!!! (which is what I was actually trying to do but used the box sample above as my real code is more complex and I wanted to isolate the issue).

Thanks again for your response and for the assistance!!! It looks like I am turning the corner from a beginner to an intermediate OO programming. :)

As for modules...I will take that fight on another day. :)

views:1752 update：2011/10/6 9:28:12


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