Modules and scrolling background / player problem

Games
#1

I am having trouble using modules to add a background and a player.

I have two files, level01.lua (contains background and level info) and gamefunctions.lua (contains the player related functions)

Basically, what I am doing is, I added the player and background into a group called bgGroup in level01.lua.
Then, based on the player’s x position, either I move the player or move bgGroup and the player together (running in opposite direction in same speed to make the player seem not moving).

Problem is, bgGroup is returning nil on line 9 of gamefunctions.lua.

It was working fine when all this was in one file but now I am trying to break it apart into smaller modules.

Am I going the wrong way in doing this?

In case, you ask why I am using velocity instead of manipulating x position, that’s because it gives me a better result in jumping (using x position, if I let go of the directional button while jumping, it stops the character from moving horizontally mid air, whereas using velocity, the player keeps moving horizontally until it lands then stops).

level01.lua

local gamefunctions = require("gamefunctions")  
  
 -- groups  
 local bgGroup = display.newGroup()  
  
 -- create objects  
 local player = gamefunctions.newPlayer(\_W \* 0.1, \_H \* 0.5)  
  
 -- objects  
 local bg\_img = display.newImageRect("bg.jpg", 960, 320)  
 bg\_img:setReferencePoint(display.TopLeftReferencePoint)  
 bg\_img.x = 0; bg\_img.y = 0  
  
 bgGroup:insert(bg\_img)  
 bgGroup:insert(player)

gamefunctions.lua

[code]
– created a player object

– actions
local function movePlayerRight(e)
vx, vy = player:getLinearVelocity()
if playerRight then
if player.x < _W * 0.5 then
player:setLinearVelocity(playerSpeedRight, vy )
elseif bgGroup.x <= -_W then
player:setLinearVelocity(playerSpeedRight, vy)
else
bgGroup.x = bgGroup.x - playerSpeedRight / 66
player:setLinearVelocity(playerSpeedRight, vy)
end
end
end

local function movePlayerLeft(e)
vx, vy = player:getLinearVelocity()
if playerLeft then
if player.x > (_W * 2) - _W * 0.5 then
player:setLinearVelocity(playerSpeedLeft, vy)
elseif bgGroup.x >= 0 then
player:setLinearVelocity(playerSpeedLeft, vy)
else
bgGroup.x = bgGroup.x - playerSpeedLeft / 66
player:setLinearVelocity(playerSpeedLeft, vy)
end
end
end
[/code] [import]uid: 39031 topic_id: 15421 reply_id: 315421[/import]

#2

Hi,

I’m new to Lua but I’ll take a stab at it. In your gamefunctions module, you need to hold a reference to the display group (bgGroup) or you can pass the display group as a parameter in your functions.

thanks, [import]uid: 44767 topic_id: 15421 reply_id: 56984[/import]

#3

Thanks for reply, marqshaw.
I got it to work by creating a new group in gamefunctions.lua and assigning it to a global variable then passing it to level01.lua.
I am not sure if this is the right way to go but it seems to work correctly… [import]uid: 39031 topic_id: 15421 reply_id: 57018[/import]