Lua read/write data in JSON format

jsonStorage.lua

-- load the JSON library.
local Json = require("json")

local JsonStorage = {}

-- Function to save a table.  Since game settings need to be saved from session to session, we will
-- use the Documents Directory
JsonStorage.saveTable = function(t, filename)
    local path = system.pathForFile( filename, system.DocumentsDirectory)
    local file = io.open(path, "w")

    if file then
        local contents = Json.encode(t)
        file:write( contents )
        io.close( file )
        return true
    else
        return false
    end
end

JsonStorage.loadTable = function(filename)
    local path = system.pathForFile( filename, system.DocumentsDirectory)
    local contents = ""
    local myTable = {}
    local file = io.open( path, "r" )

    if file then
        -- read all contents of file into a string
        local contents = file:read( "*a" )
        myTable = Json.decode(contents);
        io.close( file )
        return myTable
    end
    return nil
end

return JsonStorage

Wrong code for linux. Using system in local function will always reproduce attempt to index global 'system' (a nil value)

Because it works on Sola2D game framework i guess (which provide a system.* library)