Corona SDK data storage on simulator

Question

new to Corona SDK, and i'm trying to figure out a way to load and save a file (which stores game data) on the simulator. (i dont want to have to debug on real device and take 15 seconds just to see a variable change each time).

i followed the tutorial on here: http://www.coronalabs.com/blog/2011/08/03/tutorial-exploring-json-usage-in-corona/ and couldn't find anything on stackoverflow that already addresses this issue.

right now i have the following code for reading and storing files:

local readJSONFile = function( filename, base )

    -- set default base dir if none specified
    if not base then base = system.ResourceDirectory; end

    -- create a file path for corona i/o
    local path = system.pathForFile( filename, base )

    -- will hold contents of file
    local contents

    -- io.open opens a file at path. returns nil if no file found
    local file = io.open( path, "r" )
    if file then
       -- read all contents of file into a string
       contents = file:read( "*a" )
       io.close( file ) -- close the file after using it
    end

    return contents
end

local writeToFile = function( filename, content )
    -- set default base dir if none specified
    if not base then base = system.ResourceDirectory; end

    -- create a file path for corona i/o
    local path = system.pathForFile( filename, base )

    -- io.open opens a file at path. returns nil if no file found
    local file = io.open( path, "w" )
    if file then
       -- write all contents of file into a string
       file:write( content )
       io.close( file ) -- close the file after using it
    end
end

it seems to work because i'll read my JSON file, save it with different data, load it, and that seems to persist. HOWEVER, as soon as i close my IDE, the changes are gone. Furthermore, my actual file on my system (mac book pro) is NOT changing.

if i do:

local json = require "json"
local wordsData = json.decode( readJSONFile( "trivia.txt" ) )
wordsData.someKey = "something different"
writeToFile("trivia.txt", json.encode( wordsData ) )  -- this only works temporarily

i'm reading my trivia.txt file which is in the same directory as my main.lua and attempt to change and load something. However, the above code will NOT make the actual change to the trivia.txt on my mac book pro.

what's the proper way to do this?? i need to store game settings and game data (this is a trivia app, i need to store up to 50 words and what answer the user picked). I need to store the data in such a way that when i close my IDE, it'll remember what i wrote to file.

my guess is that when i load my trivia.txt, it's actually looking at my mac book pro for that file, every time i load up my IDE. but then when i run it on my simulator the first time, it creates a new trivia.txt in some temporary folder (which i have no idea where this is). and then it will start reading from there if i re-run the same code. right?

any help would be much appreciated!!! upvotes for more detailed answers, since i'm new to Corona SDK

Doğancan Arabacı Doğancan Arabacı · Accepted Answer · 2013-05-20T06:39:14

I suggest you to use system.DocumentsDirectory for the path. First you can read from resource directory and then you can store it in DocumentsDirectory. After that you can always look for DocumentsDirectory. This will solve your problem. Here some functions for you to be able to check if file exist or not. You can modify paths of course

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
        return false
    end
end

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

Corona SDK data storage on simulator

1 Answers