system.pathForFile() returns nil on android

Solar2D General Questions/Discussion
1

Hi everyone! I made an utility function for my game to load all of items(which are lua objects/tables) which are located inside {project folder}/Objects/Items.
Here is the code:

local lfs = require "lfs"

local itemsPath = system.pathForFile("Objects/Items", system.ResourceDirectory)

print("This is items path: " .. itemsPath)

inventoryFill = {}

function inventoryFill:fill()

    for file in lfs.dir(itemsPath) do

        local _, i = string.find(file, "%.")

        local moduleName = string.sub(file, 1, i - 1)

        if moduleName ~= "" and INVENTORY[moduleName] == nil then

            INVENTORY[moduleName] = require("Objects.Items." .. moduleName)

        end

        for k,v in pairs(INVENTORY) do

            print(k .. ' ' .. tostring(v))

        end

    end

end

return inventoryFill

It works no problem in emulator but when i run it on my android device i get an error:
InventoryFill.lua:5: attempt to concatenate local ‘itemsPath’ (a nil value)

I know that there are some restrictions when it comes working with files on android but what am i missing?

2

system.pathForFile returns path for a file not a directory unless used with nil

this code can iterate and delete through files inside folders

local lfs = require "lfs";
 
    local doc_dir2 = system.DocumentsDirectory;
    local doc_path = system.pathForFile("", doc_dir2);
    local resultOK, errorMsg;
     
    for file in lfs.dir(doc_path) do
        local theFile = system.pathForFile(file, doc_dir2);

        if file=="name of your file here" then
          resultOK, errorMsg = os.remove(theFile);
        end
    end
3

So if i can understand you cant get a path for a subfolder on android as there arent any actual folders? Ill have to rethink my logic then…

4

In Android, to use system.ResourceDirectory with system.pathForFile you’ll need to know the file name to fetch. In which case, you’re better off generating the file list beforehand and avoid using lfs post build if you don’t want to add the “require” manually.

5

Yeah i tried to avoid that but i guess it has to be done

6

Anyway if anybody has similar problems i did it like so:

  1. In the main.lua file check if the game is run on simulator
      if system.getInfo("environment") == "simulator" then
  1. If it is then generate json file with all the files inside the folder
    local lfs = require "lfs"
        local items = {}
        local j = 0
        local itemsPath = system.pathForFile("Objects/Items",
                                             system.ResourceDirectory)

        for file in lfs.dir(itemsPath) do
            local _, i = string.find(file, "%.")
            local moduleName = string.sub(file, 1, i - 1)
            if moduleName ~= "" and moduleName ~= "." and moduleName ~= ".." then
            items[moduleName] = moduleName
            end
            j = j + 1
        end

        local items_json = json.encode(items)
        local res_path = system.pathForFile("")
        local items_file, err = io.open(res_path .. "/items.json", "w")
        if not items_file then
            print("error with opening file: " .. err)
        else
            items_file:write(items_json)
        end

3.Now load everything you need from that json, in my case i wanted to load all the modules

    local items_path = system.pathForFile("items.json")
        local items_file, err = io.open(items_path, "r")
        if not items_file then
            print("Error with opening file: " .. err)
            return
        end
        local items_json = items_file:read()
        local items = json.decode(items_json)
        for _,item in pairs(items) do
            if item ~= nil and INVENTORY[item] == nil then
                INVENTORY[item] = require("Objects.Items." .. item)
            end
        end

Hope this helps someone, if you have questions DM me

7

And i think its okay to write to resource directory since we are only doing this in development on a simulator