Attempt to index global "self"(a nil value) - lua

Question

I ran this code and it gave me an error attempt to index global 'self' (a nil value), in this scene i'm creating the Question1 of the game, inside which includes creating cannon, balloons and other game elements. I checked but i'm not sure whats wrong here.
function scene.createScene()
local group = self.view ---line 27 where i got the error
scoreText = display.newText( "0", 0, 0, globals.font.bold, 32 )
scoreText.x = display.contentCenterX
scoreText.y = 32
group:insert( scoreText )
background = display.newImage( "bkg_clouds.png")
group:insert(background)
background.x = 240
background.y = 195
questionText = display.newText('a', display.contentCenterX, display.contentWidth/4, native.systemFont, 40)
group:insert(questionText)
infoBar = display.newImage ("infoBar.png")
group:insert(infoBar)
background.x = 200
background.y = 100
restartBtn = display.newImage ("restartBtn.png")
group:insert(restartBtn)
background.x = 470
background.y = 300
cannon = display.newImage ("cannon.png")
group:insert(cannon)
background.x = 10
background.y = 270
cannon.anchorX = 0.5
cannon.anchorY = 0.5
restartBtn.isVisible = true
function createBalloons(a, b)
for i = 1, a do
for j = 1, b do
local balloon = display.newImage ('balloon_fat_red.png', 465+ (i * 30), 80 + (j * 50))
balloon.balloonText1 = display.newText(hiragana_array[x+1], 495, 125)
balloon.balloonText2 = display.newText(hiragana_array[x+2], 495, 175)
balloon.balloonText3 = display.newText(hiragana_array[x+3], 495, 225)
balloon.balloonText1:setFillColor( 1,1, 0 )
balloon.balloonText2:setFillColor( 1,1, 0 )
balloon.balloonText3:setFillColor( 1,1, 0 )
balloon.name = 'balloon'
physics.addBody(balloon)
balloon.bodyType = 'static'
table.insert(balloons, balloon)
end
end
target.text = #balloons
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 = 1
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 = false
cannon.rotation = 0
local 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(dir, impulse, cannonBall.x, cannonBall.y )
--Collision listener
cannonBall:addEventListener ('collision', ballCollision)
end
end
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
cannonBall:applyLinearImpulse(dir, impulse, cannonBall.x, cannonBall.y )
--Collision listener
cannonBall:addEventListener ('collision', ballCollision)
scene.view:insert( ballCollision )
end

Answer 1

You probably need function scene:createScene(). Note the colon instead of the dot in your original code.

Answer 2

Your function should be like this.
function scene:createScene( event )
local group = self.view
-----------------------------------------------------------------------------
-- CREATE display objects and add them to 'group' here.
-- Example use-case: Restore 'group' from previously saved state.
-----------------------------------------------------------------------------
end
Here is the reference:
http://docs.coronalabs.com/api/library/storyboard/