How can i destroy all my scene objects on scene exit?

AxlFlame

Hi,
I'm having this issue and i'm getting desperate about it...

I have a game where i create many blocks and make them go from right to left via parallax effect and between them there's space for the player to draw a bridge so the character would not fall. When they exit the screen i destroy the blocks and create the new one on the right side.
I also have a pause screen from where i can exit the game and return to the title screen. My problem is that whenever i exit the scene, the physical bodies of the blocks somehow stays on the stage, even though i'm not at the game scene anymore, that is causing the game to crash if i try to draw something over the body that is already there.

How can i destroy those remaining bodies? I managed to destroy the player's character one, but i can't seem to be able to reference the bodies from the bridge and the blocks....

I tried to upload my .lua files but the forum refuses to let me lol So i'm pasting them here...

Please, any help would be deeply appreciated.

AxlFlame

Ok, so my code is too big and i can't post it either... so here goes a few parts...

This is the function that creates the blocks

newBlock = function() --this function includes all the "paths" logic. local block; --if the currentBlock needed is the first, --then we use a different image (headBlockIMG), decide the length of the new path, --decide it's distance from the previous one, and add a physics body that is as big as the whole path. if currentBlock == 1 then currentPathLen = mRandom(minPathLen, maxPathLen); dropEnemyAtBlock = mRandom(2, currentPathLen-1); block = newBitmap(BlocoIMG); block:setAnchorPoint(0.5, 0.5); sceneParent:addChild(block); if lastBlock then block:setPosition(lastBlock:getX()+mRandom(minDistWidth, maxDistWidth), mMin(minHeight,mMax(maxHeight, lastBlock:getY()+mRandom(-minDistHeight, maxDistHeight)))); else --let's set first block of the game position block:setPosition(block:getWidth()*0.5, 220); end block.body = b2World:createBody{type = b2STATIC_BODY, position = {x = block:getX(), y = block:getY()}, }; block.body.name = "block"; block.body.sprite = block; local blockShape = b2PolygonShape.new(); local blockWidth, blockHeight = block:getWidth(), block:getHeight(); blockShape:set(-blockWidth*0.5, -blockHeight*0.5, -blockWidth*0.5+blockWidth*currentPathLen, -blockHeight*0.5, -blockWidth*0.5+blockWidth*currentPathLen, blockHeight*0.5, -blockWidth*0.5, blockHeight*0.5); block.body:createFixture{shape = blockShape, friction = 0, restitution = 0, density = 10, isSensor = false }; block.removeAt = block:getWidth()*currentPathLen; function block:onEnterFrame() self:setX(self:getX()-layer1Speed); self.body:setPosition(self:getPosition()); if not self.created then if self:getX() < screenWidth then self.created = true; newBlock(); end else if self:getX() < -block.removeAt then b2World:destroyBody(self.body); self.body = nil; self:removeEventListener(Event.ENTER_FRAME, self.onEnterFrame, self); sceneParent:removeChild(self); end end end elseif currentBlock == currentPathLen then --if the block is the last of the path, then we use a "endBlockIMG". currentBlock = 0; block = newBitmap(BlocoIMG); block:setAnchorPoint(0.5, 0.5); sceneParent:addChild(block); block:setPosition(lastBlock:getX()+block:getWidth(), lastBlock:getY()); function block:onEnterFrame() self:setX(self:getX()-layer1Speed); if not self.created then if self:getX() < screenWidth then self.created = true; newBlock(); end else if self:getX() < -50 then self:removeEventListener(Event.ENTER_FRAME, self.onEnterFrame, self); sceneParent:removeChild(self); end end end else block = newBitmap(BlocoIMG); block:setAnchorPoint(0.5, 0.5); sceneParent:addChild(block); block:setPosition(lastBlock:getX()+block:getWidth(), lastBlock:getY()); function block:onEnterFrame() self:setX(self:getX()-layer1Speed); if not self.created then if self:getX() < screenWidth then self.created = true; newBlock(); end else if self:getX() < -50 then self:removeEventListener(Event.ENTER_FRAME, self.onEnterFrame, self); sceneParent:removeChild(self); end end end --we only want monsters to drop on the "middle" blocks, so here we check if we must create one, and decide randomly which one. if currentBlock == dropEnemyAtBlock then dropEnemyAtBlock = 0; local enemyType = mRandom(1, #enemyTable); local enemy = enemyTable[enemyType](enemyTexture[enemyType], block:getX(), block:getY()-(block:getHeight()*0.5), b2World); sceneParent:addChild(enemy); enemy.moveMe = function(object) local selfX, selfY = object:getPosition(); object:setPosition(selfX-layer1Speed, selfY); return b2World; end enemy:addListeners(); end end function block:removeListeners() block:removeEventListener(Event.ENTER_FRAME, block.onEnterFrame, block); end function block:addListeners() block:addEventListener(Event.ENTER_FRAME, block.onEnterFrame, block); end currentBlock = currentBlock+1; block:addEventListener(Event.ENTER_FRAME, block.onEnterFrame, block); lastBlock = block; end

AxlFlame

This is the init from my game scene, it includes the function i use to allow the gestures recognition with the help of the Gestures.lua file.

--on scene initialization function bonecosDesenho:init()   if sets.music then music.channel = music.minigamesDesenho:play(0,1000000) end   -- Resetando alguns valores lastBlock = nil; currentBlock = 1; currentScore = 0; --currentLifes = 3;   enemyTable = {bDobstaculos.new, bDobstaculos.new};   --create world instance b2World = b2.World.new(0, 18, true) b2PolygonShape = b2.PolygonShape; b2STATIC_BODY = b2.STATIC_BODY;   _G.b2World = b2World; sceneParent = self; createParallaxBG(); newBlock(); currentPathLen = 20;   --Criando e guardando referência pro boneco self.boneco = self:boneco(100, 100)   --Recreating first block body due to the manual change in pathLen b2World:destroyBody(lastBlock.body); lastBlock.body = b2World:createBody{type = b2STATIC_BODY, position = {x = lastBlock:getX(), y = lastBlock:getY()}, }; local blockShape = b2PolygonShape.new(); blockShape:set(-lastBlock:getWidth()*0.5, -lastBlock:getHeight()*0.5, -lastBlock:getWidth()*0.5+lastBlock:getWidth()*currentPathLen, -lastBlock:getHeight()*0.5, -lastBlock:getWidth()*0.5+lastBlock:getWidth()*currentPathLen, lastBlock:getHeight()*0.5, -lastBlock:getWidth()*0.5, lastBlock:getHeight()*0.5); lastBlock.body:createFixture{shape = blockShape, friction = 0, restitution = 0, density = 10, isSensor = false }; lastBlock.removeAt = lastBlock:getWidth()*currentPathLen; lastBlock.body.name = "block"; lastBlock.body.sprite = lastBlock; dropEnemyAtBlock = 0;   --set up debug drawing --[[local debugDraw = b2.DebugDraw.new() self.world:setDebugDraw(debugDraw) self:addChild(debugDraw)--]]   --Adding the score objScore = GCscore.new({Texture.new("images/0.png"), Texture.new("images/1.png"), Texture.new("images/2.png"), Texture.new("images/3.png"), Texture.new("images/4.png"), Texture.new("images/5.png"), Texture.new("images/6.png"), Texture.new("images/7.png"), Texture.new("images/8.png"), Texture.new("images/9.png")}, 25); self:addChild(objScore); objScore:setX(screenWidth-30); objScore:setScore(100); objScore:setScore(20);   --adding the pause button local pauseButton = GCpauseBut.new(newTexture("Buttons/PauseSmall.png")); self:addChild(pauseButton); pauseButton:setPosition(screenWidth*0.01, 4);   --=================================================== -- GESTOS --===================================================   --Shape para servir de scopo do verificador de gestos local areaGestos = Shape.new() areaGestos:setFillStyle(Shape.SOLID, 0xC0C0C0, 0.5) areaGestos:beginPath(Shape.NON_ZERO) areaGestos:moveTo(0, 195) areaGestos:lineTo(application:getContentWidth(), 195) areaGestos:lineTo(application:getContentWidth(), 225) areaGestos:lineTo(0, 225) areaGestos:lineTo(0, 195) areaGestos:endPath() self:addChild(areaGestos)   local font = TTFont.new("Fontes/tahoma.ttf", 20)   local myText = TextField.new(font, "Result: ") myText:setPosition(50,50) self:addChild(myText)   self.gest = Gestures.new({ debug = true, draw = true, drawColor = 0xff0000, drawWidth = 5, autoTrack = true, scope = areaGestos, allowRotation = true, inverseShape = true, points = 33 })   self.callback = function(name) local debugDraw = b2.DebugDraw.new() b2World:setDebugDraw(debugDraw) stage:addChild(debugDraw) myText:setText(name) --Update local xIni = self.gest.points[1].x; local xFim = self.gest.points[#self.gest.points].x; local yIni, yFim = 196, 225; --Apaga o ultimo shape para recriar bridge:clear() if bridge.body then b2World:destroyBody(bridge.body) end --Criando novo shape bridge:setFillStyle(Shape.SOLID, 00000000, 0.5) bridge:beginPath(Shape.NON_ZERO) --calculate drawn width local width = self.gest.points[#self.gest.points].x - self.gest.points[1].x print(self.gest.points[#self.gest.points].x, self.gest.points[1].x) --drawing shape from 0 coordinates bridge:moveTo(0, yIni) bridge:lineTo(width, yIni) bridge:lineTo(width, yFim) bridge:lineTo(0, yFim) bridge:lineTo(0, yIni) bridge:endPath() areaGestos:addChild(bridge) --adding to expected position bridge:setX(self.gest.points[1].x) --if drawing from left to right if self.gest.points[1].x < self.gest.points[#self.gest.points].x then bridge.left2right = true else bridge.left2right = false end   bridge:setY(yFim/yIni)   --Criando corpo fisico p/ ponte bridge.body = b2World:createBody{type = b2STATIC_BODY, position = {x = xFim/xIni, y = yFim-4}, }; bridge.body.name = "bridge"; local bridgeShape = b2.PolygonShape.new() local bridgeWidth = bridge:getWidth() local bridgeHeight = bridge:getHeight() bridgeShape:set(-bridgeWidth, -bridgeHeight, -bridgeWidth+bridgeWidth, -bridgeHeight, -bridgeWidth+bridgeWidth, bridgeHeight, -bridgeWidth, bridgeHeight); bridge.body:createFixture{shape = bridgeShape, friction = 0, restitution = 0, density = 10, isSensor = false }; local teste = bridge:getX() print (teste) --you don't need to define same methods all the time --and certainly don't need to add onEnterFrame event on each callback --there will be multiple on Enter frame events if not bridge.onEnterFrame then --movendo o shape e o corpo function bridge:onEnterFrame() --calculate new bridge x local bridgeX = bridge:getX()-3 --change bridge position bridge:setX(bridgeX) if bridge.left2right then bridgeX = bridgeX + bridge:getWidth() end --if bridge x has body if bridge.body then --set bodies position alongside with bridge local _, bodyY = bridge.body:getPosition() bridge.body:setPosition(bridgeX, bodyY) end if bridge:getX() < -480 then bridge:clear() bridge:removeListeners() end end function bridge:removeListeners() bridge:removeEventListener(Event.ENTER_FRAME, bridge.onEnterFrame, bridge); end function bridge:addListeners() bridge:addEventListener(Event.ENTER_FRAME, bridge.onEnterFrame, bridge); end bridge:addEventListener(Event.ENTER_FRAME, bridge.onEnterFrame, bridge); end end   self.gest:addGesture("Line", { {x = 0, y = 0}, {x = 0, y = 100} }, self.callback)   self.gest:addGesture("ZigZag", { {x = 0, y = 0}, {x = 50, y = 87}, {x = 100, y = 0}, {x = 150, y = 87}, }, callback)   local x = 0 local y = -100 local circle = {} local totalPoints = 72 local step = (math.pi*2)/totalPoints   for angle = 1, totalPoints do local newX = x*math.cos(angle*step)-y*math.sin(angle*step) local newY = y*math.cos(angle*step)+x*math.sin(angle*step) local point = {x = newX, y = newY} table.insert(circle, point) end   self.gest:addGesture("Circle", circle, callback)   --=================================================== -- FIM GESTOS --=================================================== --run world self:addListeners(); self:addEventListener(Event.REMOVED_FROM_STAGE, self.removedFromStage, self); self:addEventListener(Event.ENTER_FRAME, self.onEnterFrame, self) --remove event on exiting scene self:addEventListener("exitBegin", self.onExitBegin, self) end

AxlFlame

And finally this is the function i was able to use to destroy the character's body.

--removing event on exiting scene function bonecosDesenho:onExitBegin() print("oi") b2World:destroyBody(self.boneco.body); sceneParent = nil; self:removeEventListener(Event.ENTER_FRAME, self.onEnterFrame, self) end

john26

Can you show the code where you destroy the blocks and bridges? Your function bonecosDesenho:onExitBegin() looks fine. You need to do the same thing for the other objects...

AxlFlame

So, i wasn't actually destroying the bridge body, but I added this to the onExitBegin and it worked.

function BonecosDesenho:onExitBegin() b2World:destroyBody(self.boneco.body); b2World:destroyBody(bridge.body); sceneParent = nil; self:removeEventListener(Event.ENTER_FRAME, self.onEnterFrame, self) end

If I try to follow that line and use this:

b2World:destroyBody(block.body);

It gives me this error:
attempt to index global 'block' (a nil value)

Sorry for taking so long... any help would be deeply appreciated.

hgvyas123

It gives me this error:
attempt to index global 'block' (a nil value)

generally this error will come when you are trying to access object which is already removed or that is a local inside any function[and hence not accessible where you are trying to access] if you are sure that it is not removed then you might have declared it as local in any other function try to remove that local and make that global after this every thing should work fine

also in the case you want to delete everything onExitBegin use this

for i=self:getNumChildren(),1,-1 do local sprite = self:getChildAt(i) if sprite.body then   world:destroyBody(sprite.body) end sprite:removeFromParent()--usually it will not needed as scenemanager do this for you end

AxlFlame

Ok, i'm sorry for the dumb question, but to make the variable global, I simply need to remove the 'local' before? Indeed the block is being created as local inside the NewBlock function.
Assuming its that, I got another error:

"attempt to perform arithmetic on field 'removeAt' (a nil value)"

removeAt is a property of block, and after I tried to change block to global aparrently it started to receive nil...
That block.removeAt is located inside the NewBlock function I pasted here, halfway, right before the block onEnterFrame.

Btw, thanks for the advice regarding destroying everything! It works perfectly... except for the block of course =/

AxlFlame

So, I tried switching back block to local block as I noticed that the problem is not that the blocks aren't being destroyed, its the bridge that isn't... at least using your code for destroying everything on the scene.

That said I tried to use this to destroy the bridge:

b2World:destroyBody(bridge.body);

But when I try that, and go to start this game scene again it says:

Body is already destroyed.

And the error points to this part:

if bridge.body then b2World:destroyBody(bridge.body) end

What I don't understand is why do I get this error, if the 'if' is exactly to avoid that?