How to design a "Dynamic inventory system" for a point and click game? - lua

Question

I have done lots of research on invetory system for point and click game in Lua and corona.
I have come across this example,I am doing something similar to this,but I need a dynamic inventory system.
I mean if I have 4 slots,and all them are full the fifth object go to next slot,so there will be an arrow to the right so I can click on ;and go to the next page.
And imagine there are 5 items,and I have 4 slots,the fifth slot would be on the next page.
I use the third item,and third slot would then be empty,so I want the fourth and fifth item automatically move back to third and fourth slot.
I have hard time figuring this out.
Thanks for advance.
local myInventoryBag={}
local maxItems = 10 -- change this to how many you want
myInventoryBag[5]=3 -- Hammer for instance
myInventoryBag[4]=7 -- A metal Pipe for instance
local function getImageForItem(thisItem)
local itemNumber = tonumber(thisItem)
local theImage=""
if itemNumber==3 then
theImage="hammer.png"
elseif itemNumber == 7 then
theImage="metalpipe.png"
elseif ... -- for other options
...
else
return nil
end
local image = display.newImage(theImage)
return image
end
local function displayItems()
local i
for i=1,#myInventoryBag do
local x = 0 -- calculate based on the i
local y = 0 -- calculate based on the i
local image = getImageForItem(myInventoryBag[i])
if image==nil then return end
image.setReferencePoint(display.TopLeftReferencePoint)
image.x = x
image.y = y
end
end

Answer 1

local itemImages =
{
[0] = display.newImage('MISSING_ITEM_IMAGE.PNG'),
[3] = display.newImage('hammer.png'),
[7] = display.newImage('metalpipe.png'),
}
function getImageForItem(itemId)
return itemImages[itemId] or itemImages[0]
end
local myInventoryBag={}
local maxItems = 10 -- change this to how many you want
local visibleItems = 4 -- show this many items at a time (with arrows to scroll to others)
-- show inventory items at index [first,last]
local function displayInventoryItems(first,last)
local x = 0 -- first item goes here
local y = 0 -- top of inventory row
for i=first,last do
image = getImageForItem(myInventoryBag[i])
image.x = x
image.y = y
x = x + image.width
end
end
-- show inventory items on a given "page"
local function displayInventoryPage(page)
page = page or 1 -- default to showing the first page
if page > maxItems then
-- error! handle me!
end
local first = (page - 1) * visibleItems + 1
local last = first + visibleItems - 1
displayInventoryItems(first, last)
end
myInventoryBag[5] = 3 -- Hammer for instance
myInventoryBag[4] = 7 -- A metal Pipe for instance
displayInventoryPage(1)
displayInventoryPage(2)

Answer 2

Basically what you would do is loop through all the inventory slots and check if the slot is empty. If it's empty, place the item in that slot and stop the loop. If it's not, go to the next one.
If you want to remove an item from the inventory, you can simply call table.delete(myInventoryBag, slotToEmpty).
For pages, you'd simply have a page variable. When drawing the inventory slots, just loop from slots (page-1) * 4 + 1 to page * 4.
(Edit: I'd highly recommend using proper indentation, as it will make the code much much more readable.)