Scenes and groups trouble using Lua and Corona SDK - lua

Question

My buttons and scene changes are bugging, the buttons on my titlescreen scene bellow both work and direct to the appropriate screens, but they will only do it once. So I cannot naviagte to options, then back to the the title screen, then back to options again - and I cannot work out why?
Here is my titlescreen file:
module(..., package.seeall)
local assetPath = "assets/"
local mainGroup = display.newGroup()
function new()
local ui = require("ui")
local titleScreen = display.newImageRect(assetPath .. "mainMenu.png", display.contentWidth, display.contentHeight)
titleScreen.x = display.contentWidth / 2
titleScreen.y = display.contentHeight / 2
mainGroup:insert(titleScreen)
local onPlayTouch = function( event )
if event.phase == "release" then
director:changeScene("gameScreen")
end
end
local playButton = ui.newButton{
defaultSrc = assetPath .. "playnowbtn.png",
defaultX = 222,
defaultY = 62,
overSrc = assetPath .. "playnowbtn-over.png",
overX = 222,
overY = 62,
onEvent = onPlayTouch
}
playButton.x = display.contentWidth / 2
playButton.y = 50;
mainGroup:insert( playButton )
local onOptionTouch = function( event )
if event.phase == "release" then
director:changeScene("optionsScreen")
end
end
local optionButton = ui.newButton{
defaultSrc = assetPath .. "playnowbtn.png",
defaultX = 222,
defaultY = 62,
overSrc = assetPath .. "playnowbtn-over.png",
overX = 222,
overY = 62,
onEvent = onOptionTouch
}
optionButton.x = display.contentWidth / 2
optionButton.y = 190;
mainGroup:insert( optionButton )
return mainGroup
end
My options file looks like this :
module(..., package.seeall)
function new()
local assetPath = "assets/"
local localGroup = display.newGroup()
local background = display.newImage (assetPath .."optionsScreen.png")
localGroup:insert(background)
local onBackTouch = function( event )
if event.phase == "release" then
director:changeScene("titleScreen")
end
end
local backButton = ui.newButton{
defaultSrc = assetPath .. "playnowbtn.png",
defaultX = 222,
defaultY = 62,
overSrc = assetPath .. "playnowbtn-over.png",
overX = 222,
overY = 62,
onEvent = onBackTouch
}
backButton.x = display.contentWidth / 2
backButton.y = display.contentHeight / 2
localGroup:insert(backbutton)
return localGroup
end
Now the button is displayed on the options scene and responds to touch, but does not direct back to the titlescreen.
I think I am getting confused with groups and only assigning images to scenes not the whole game?
Can anyone help me out, Thanks.
EDIT:
I'm also getting these runtime errors when clicking the buttons.
Runtime error
/Users/Lewis/Desktop/proj/optionsScreen.lua:30: ERROR: table expected. If this is a function call, you might have used '.' instead of ':'
stack traceback:
[C]: ?
[C]: in function 'insert'
/Users/Lewis/Desktop/proj/optionsScreen.lua:30: in function 'new'
/Users/Lewis/Desktop/proj/director.lua:118: in function 'loadScene'
/Users/Lewis/Desktop/proj/director.lua:415: in function 'changeScene'
/Users/Lewis/Desktop/proj/titlescreen.lua:67: in function 'onEvent'
/Users/Lewis/Desktop/proj/ui.lua:94: in function
?: in function
Runtime error
/Users/Lewis/Desktop/proj/director.lua:151: attempt to call field 'unloadMe' (a nil value)
stack traceback:
[C]: in function 'unloadMe'
/Users/Lewis/Desktop/proj/director.lua:151: in function '_listener'
?: in function
?: in function

Answer 1

I don't use director.lua myself so I'm not 100% sure, but in your options.lua you put the following two lines inside the new() function:
local assetPath = "assets/"
local localGroup = display.newGroup()
However in your titlescreen.lua those lines are above the new() function, and I think that's how it needs to be.
In general you should make your indentation consistent, so that it's easy to notice which code is inside which code-blocks.

Answer 2

In your error print-out, it's asking for an unload me function.
Try adding this to your code (above the return statement) and see if it makes a difference:
function unloadMe()
print( "test" )
end
And see if that gets rid of the error. Another option is to ditch ui.lua and use the new widget library's widget.newButton() function instead. Here's the doc page for that (syntax is almost the same as what you already have, so shouldn't be much changes necessary):
http://developer.anscamobile.com/reference/index/widgetnewbutton