physics doesn't work in lua - lua

Question

This code creates a cannon and 3 balloons, the cannon should shoot out a bullet that'll destroy balloons, along with the words. DUring the process the cannon should rotate and when i release my finger from the screen it shoots. For some reason it doesn't respond, cannon not rotating nor any bullet is shot.
local score = 0
local scoreText
local scoreForLevelComplete
local background
local infoBar
local restartBtn
local cannon
local levelNum
local cannonCharge = {}
local shot = {}
local cannonBall
local impulse = 0
local balloons = {}
local cannonCharge = {}
local shot = {}
function scene:createScene(event)
local group = self.view
background = display.newImage( "bkg_clouds.png")
group:insert(background)
background.x = 230
background.y = 195
scoreText = display.newText( "0", 0, 0, native.systemFont, 32 )
scoreText:setFillColor( 0,0, 0 )
scoreText.x = 87
scoreText.y = 28
group:insert( scoreText )
questionText = display.newText('a', display.contentCenterX, display.contentWidth/4, native.systemFont, 40)
group:insert(questionText)
infoBar = display.newImage ("infoBar.png")
group:insert(infoBar)
infoBar.x = 10
infoBar.y = 25
restartBtn = display.newImage ("restartBtn.png")
group:insert(restartBtn)
restartBtn.x = 470
restartBtn.y = 300
cannon = display.newImage ("cannon.png")
group:insert(cannon)
cannon.x = 10
cannon.y = 270
cannon.anchorX = 0.5
cannon.anchorY = 0.5
restartBtn.isVisible = true
local balloon = display.newImage ('balloon_fat_red.png', 495, 125)
group:insert(balloon)
balloon = display.newImage ('balloon_fat_red.png', 495, 175)
group:insert(balloon)
balloon = display.newImage ('balloon_fat_red.png', 495, 225)
group:insert(balloon)
local balloonText1 = display.newText('\227\129\130', 495, 125)
balloonText1:setFillColor( 1,1, 0 )
local balloonText2 = display.newText('\227\129\132', 495, 170)
balloonText2:setFillColor( 1,1, 0 )
local balloonText3 = display.newText('\227\129\134', 495, 225)
balloonText3:setFillColor( 1,1, 0 )
balloon.name = 'balloon'
physics.addBody(balloon)
balloon.bodyType = 'static'
table.insert(balloons, balloon)
group:insert(balloonText1)
group:insert(balloonText2)
group:insert(balloonText3)
function ballCollision(e)
if (e.other.name == 'balloon') then
scene.updateScore()
e.target:removeSelf()
print ('remove balloon text')
e.other:removeSelf()
audio.play(pop)
end
end
function cannonCharge:touch(e)
if(e.phase == 'began') then
impulse = 0
cannon.isVisible = true
Runtime:addEventListener('enterFrame', charge)
end
end
function charge()
local degreesPerFrame = 0.5
cannon.rotation = cannon.rotation - degreesPerFrame
impulse=impulse-0.2
if(cannon.rotation < -46) then
cannon.rotation = -46
impulse = -3.2
end
end
function shot:touch(e)
if(e.phase == 'ended') then
Runtime:removeEventListener('enterFrame', charge)
cannon.isVisible = true
cannon.rotation = 0
cannonBall = display.newImage('cannon ball.png', 84, 220)
physics.addBody(cannonBall, {density = 1, friction = 0, bounce = 0})
group:insert(cannonBall)
-- Shoot cannon ball
cannonBall:applyLinearImpulse(3, impulse, cannonBall.x, cannonBall.y )
--Collision listener
cannonBall:addEventListener ('collision', ballCollision)
end
end
end
This is my enterscene function
function scene:enterScene( event )
local group = self.view
background:addEventListener('touch', cannonCharge)
background:addEventListener('touch', shot)
end

Answer 1

I know the Corona docs say that listener can be a table object when call addEventListener('event', listener) but I have never seen or used that. There is no advantage in posted code to have functions defined inside the createScene since they are global and you already have a bunch or module-local variables. Try pulling the listeners out and making them regular functions:
local canon
...
local cannonCharge = function(event)
if event.phase == 'began' then
impulse = 0
cannon.isVisible = true
Runtime:addEventListener('enterFrame', charge)
end
end
local shot = function(event)
...
end
local function charge()
...
end
... other local functions ...
function scene:createScene(event)
...
end
Also, confirm that your touch listeners are being called by printing something inside each one.
Finally, and most importantly, you only added the last balloon to the physics so the bullet can only collide with that one balloon. The same way that you had to add group:insert(balloon) after each balloon created, you should have physics.addBody(balloon, ...) after each group insert. So do this:
local balloon1 = display.newImage ('balloon_fat_red.png', 495, 125)
local balloon2 = display.newImage ('balloon_fat_red.png', 495, 175)
local balloon3 = display.newImage ('balloon_fat_red.png', 495, 225)
group:insert(balloon1)
group:insert(balloon2)
group:insert(balloon3)
physics.addBody(balloon1)
physics.addBody(balloon2)
physics.addBody(balloon3)
balloon1.bodyType = 'static'
balloon2.bodyType = 'static'
balloon3.bodyType = 'static'
table.insert(balloons, balloon1)
table.insert(balloons, balloon2)
table.insert(balloons, balloon3)
There is a lot of code duplication there, and adding more balloons requires many lines to change, so you might as well factor out the duplicate code into a function:
local function createBalloon(x, y)
local balloon = display.newImage ('balloon_fat_red.png', x, y)
group:insert(balloon)
physics.addBody(balloon)
balloon.bodyType = 'static'
table.insert(balloons, balloon)
end
createBalloon(495, 125)
createBalloon(495, 175)
createBalloon(495, 225)
which has the advantage that if you need more balloon you won't forget any settings, and any new settings put in createBallon so all balloons have same config (except for function parameters like x,y etc).
Update: Determine which balloon in collision handler
Depends why you need to know which of the balloons. For example if it's because balloon 1 gives 10 pts while 3 gives 30, then there are better ways: you can add your fields to objects, like you could have balloon1.points = 10, balloon2.points = 30 etc (you would make that a function argument of createBalloon) and in collision handler just use score = score + e.other.points. You should only need to use Local Collision Handling because only need to know when the cannon ball collides with balloons. To figure out if e.other is a balloon, easiest is to add a property when you create balloon:
local function createBalloon(x, y, balloonText)
local balloon = ...
...
balloon.isBalloon = true -- only balloon objects will have this
balloon.label = balloonText
end
Couple notes on the above: another custom property is label since you want to remove the balloon text in the collision handler, easiest is to have a property for it. But do not remove objects involved in collision in the collision handler, as explained in that document, use delayed removal. So your handler becomes
function ballCollision(e)
if e.other.isBalloon then
scene.updateScore(e.other.points)
timer.performWithDelay(1, e.target.removeSelf, e.target)
timer.performWithDelay(1, e.other.removeSelf, e.target)
e.other.label:removeSelf() -- this is ok: not involved in collision
audio.play(pop)
end
end

Answer 2

You have declared balloons as a array and using the balloon
as a variable while assigning images to them. So you need to declare 3 separate balloon object like balloon text or if you are using array then you need to declare like this.
for i=1,3 do
balloon[i] = display.newImage ('balloon_fat_red.png', 495, 225)
group:insert(balloon[i])
end
So it will identify which balloon you want to shoot.