Attempt to index local (a boolean value)

Question

I have 2 different Lua files, main.lua and game_model.lua. I'm trying to save some details in a JSON file (I googled that using a JSON file would be the best way to save a user's settings and score), but I'm getting the following error:

Error: File: main.lua Line: 11 Attempt to index local 'game' (a boolean value)

Why is am I getting this error and how can fix it?

Here is the code in my main.lua:

--Main.lua

display.setStatusBar( display.HiddenStatusBar )

local composer = require( "composer" )
local game = require("data.game_model")

myGameSettings = {}
myGameSettings.highScore = 1000
myGameSettings.soundOn = true
myGameSettings.musicOff = true
myGameSettings.playerName = "Andrian Gungon"
game.saveTable(myGameSettings, "mygamesettings.json")

composer.gotoScene("scripts.menu")

game_model.lua (in the data subdirectory) contains this code:

--game_model.lua (located at data/game_model.lua)

local json = require("json")

function saveTable(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
        print( "Error!" )
        return false
    end
end

function loadTable(filename)
    local path = system.pathForFile( filename, system.DocumentsDirectory)
    local contents = ""
    local myTable = {}
    local file = io.open( path, "r" )
    if (file) then         
         local contents = file:read( "*a" )
         myTable = json.decode(contents);
         io.close( file )
         return myTable 
    end
    return nil
end

Indore

Answer 1

It means that the module data.game_model did not return anything when it was loaded.
In this case, require returns true.

Masturbation

Answer 2

To fix the problem identified in lhf's answer, you can put your table saving and loading functions in a table that is returned by data.game_model, like this:

-- Filename: data/game_model.lua

local model = {}

local json = require("json")

function model.saveTable( t, filename )
    -- code for saving
end

function model.loadTable( filename )
    -- code for loading
end

return model

Note also that a common mistake would be to declare the functions as model:saveTable( t, fn ) instead of model.saveTable( t, fn ). Remember, the former is syntactic sugar for model.saveTable( model, t, fn ).

Now the variable game in local game = require( "data.game_model" ) should be initialized to a table containing your functions. You can easily check this:

local game = require("data.game_model")

print( type( game ) )
for k,v in pairs(game) do
    print(k,v)
end 

Produces output like:

table
loadTable   function: 0x7f87925afa50
saveTable   function: 0x7f8794d73cf0

Heffernan

Answer 3

Use code below to save/load. All code comes from github/robmiracle.

local M = {}
local json = require("json")
local _defaultLocation = system.DocumentsDirectory
local _realDefaultLocation = _defaultLocation
local _validLocations = {
   [system.DocumentsDirectory] = true,
   [system.CachesDirectory] = true,
   [system.TemporaryDirectory] = true
}

function M.saveTable(t, filename, location)
    if location and (not _validLocations[location]) then
     error("Attempted to save a table to an invalid location", 2)
    elseif not location then
      location = _defaultLocation
    end

    local path = system.pathForFile( filename, location)
    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

function M.loadTable(filename, location)
    if location and (not _validLocations[location]) then
     error("Attempted to load a table from an invalid location", 2)
    elseif not location then
      location = _defaultLocation
    end
    local path = system.pathForFile( filename, location)
    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

function M.changeDefault(location)
    if location and (not location) then
        error("Attempted to change the default location to an invalid location", 2)
    elseif not location then
        location = _realDefaultLocation
    end
    _defaultLocation = location
    return true
end

function M.print_r ( t ) 
    local print_r_cache={}
    local function sub_print_r(t,indent)
        if (print_r_cache[tostring(t)]) then
            print(indent.."*"..tostring(t))
        else
            print_r_cache[tostring(t)]=true
            if (type(t)=="table") then
                for pos,val in pairs(t) do
                    if (type(val)=="table") then
                        print(indent.."["..pos.."] => "..tostring(t).." {")
                        sub_print_r(val,indent..string.rep(" ",string.len(pos)+8))
                        print(indent..string.rep(" ",string.len(pos)+6).."}")
                    elseif (type(val)=="string") then
                        print(indent.."["..pos..'] => "'..val..'"')
                    else
                        print(indent.."["..pos.."] => "..tostring(val))
                    end
                end
            else
                print(indent..tostring(t))
            end
        end
    end
    if (type(t)=="table") then
        print(tostring(t).." {")
        sub_print_r(t,"  ")
        print("}")
    else
        sub_print_r(t,"  ")
    end
    print()
end

M.printTable = M.print_r

return M 

Usage

local loadsave = require("loadsave")

myTable = {}
myTable.musicOn = false
myTable.soundOn = true

loadsave.saveTable(myTable, "myTable.json")

Rubinrubina

Thanks for your answer ... :) – Voyageur