Error: Attempt to index global 'fifteenButton' (a nil value) - button

Question

Error Line: 92
Attempt to index global 'fifteenButton' (a nil value)
stack traceback:
[C]: ?
/Users/ejaytumacder/dev/HappyShaker/time_select.lua:92: in function </Users/ejaytumacder/dev/HappyShaker/time_select.lua:90>
?: in function 'dispatchEvent'
?: in function '?'
?: in function 'gotoScene'
/Users/ejaytumacder/dev/HappyShaker/time_select.lua:12: in function '_onRelease'
?: in function '?'
?: in function <?:406>
?: in function <?:218>
This is the error I get above, and below is the code that it originates from.
local storyboard = require("storyboard")
local widget = require("widget")
local scene = storyboard.newScene()
local mydata = require("mydata")
local function fifteenSecondButtonEvent( event )
local phase = event.phase
if "ended" == phase then
mydata.time = 15
storyboard.gotoScene("play")
end
end
local function thirtySecondButtonEvent( event )
local phase = event.phase
if "ended" == phase then
mydata.time = 30
storyboard.gotoScene("play")
end
end
local function sixtySecondButtonEvent( event )
local phase = event.phase
if "ended" == phase then
mydata.time = 60
storyboard.gotoScene("play")
end
end
function scene:createScene( event )
local group = self.view
local timeText = display.newText("TIME", 160, 70, "Helvetica", 30)
group:insert( timeText )
local fifteenButton = widget.newButton {
time = 15,
left = 75,
top = 150,
width = 164,
height = 42,
defaultFile = "fifteen_button.png",
overFile = "fifteen_button_pressed.png",
label = "",
onRelease = fifteenSecondButtonEvent
}
--group:insert(fifteenButton)
local thirtyButton = widget.newButton {
time = 30,
left = 75,
top = 250,
width = 164,
height = 42,
defaultFile = "thirty_button.png",
overFile = "thirty_button_pressed.png",
label = "",
onRelease = thirtySecondButtonEvent
}
--group:insert(thirtyButton)
local sixtyButton = widget.newButton {
time = 60,
left = 75,
top = 350,
width = 164,
height = 42,
defaultFile = "sixty_button.png",
overFile = "sixty_button_pressed.png",
label = "",
onRelease = sixtySecondButtonEvent
}
group:insert(fifteenButton)
group:insert(thirtyButton)
group:insert(sixtyButton)
print( "Number of children in Display Group: " .. group.numChildren )
end
function scene:willEnterScene( event )
local group = self.view
end
function scene:enterScene( event )
local group = self.view
end
function scene:exitScene( event )
local group = self.view
fifteenButton:removeEventListener( 'onRelease', fifteenSecondButtonEvent ) -- line 92
thirtyButton:removeEventListener( 'onRelease', thirtySecondButtonEvent )
sixtyButton:removeEventListener( 'onRelease', sixtySecondButtonEvent )
timeText:removeSelf()
timeText = nil
if fifteenButton then
fifteenButton:removeSelf()
fifteenButton = nil
end
if thirtyButton then
thirtyButton:removeSelf()
thirtyButton = nil
end
if sixtyButton then
sixtyButton:removeSelf()
sixtyButton = nil
end
display.remove(group)
storyboard.removeScene( "time_select" )
end
function scene:destroyScene( event )
local group = self.view
end
scene:addEventListener("createScene", scene)
scene:addEventListener("willEnterScene", scene)
scene:addEventListener("enterScene", scene)
scene:addEventListener("exitScene", scene)
scene:addEventListener("destroyScene", scene)
return scene

Answer 1

So your question has two problems going on. I'm going to address why you're getting that error.
You are getting that error on line 92 because you are defining fifteenButton in the createScene function. as a local object. So it can't be referenced outside the createScene function. To fix that issue you should add local fifteenButton, thirtyButton, sixtyButton to the top of the file. Then remove the local from before the same named variables in the createScene. This will fix your error.