Creating a save function

nil · June 21, 2016, 12:52am

I have been with lua for almost two years now but I have never worked with io. How would I go about creating a save function that would require an array/dictionary to be passed to it and it would add it to a JSON array in a text file named “SaveFile.txt” and if its their first time saving the data it would create a blank JSON array. The best I have came up with was this

json = require "json" local path = system.pathForFile("SaveFile.txt", system.DocumentsDirectory) &nbsp; function save(dataTable) &nbsp; &nbsp; &nbsp;file = io.open(path, "w") &nbsp; &nbsp; &nbsp;if file then &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; contents = file:read() or "[]" &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; encodedJson = json.encode(table.insert(json.decode(contents),dataTable)) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; file:write(encodedJson) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; file:close() &nbsp; &nbsp; &nbsp;else &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; print("File does not exist") &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; file:write("[]") &nbsp; &nbsp; &nbsp;end end

nil · June 21, 2016, 12:54am

Note* all it does is creates a text file with the source of “null”

nil · June 21, 2016, 3:20am

I worked on it a little bit more and now I believe I just have a logic error now.

local path = system.pathForFile("SaveFile2.txt", system.DocumentsDirectory) &nbsp; json = require "json" &nbsp; function save(dataTable) &nbsp; &nbsp; &nbsp;file = io.open(path, "r+") &nbsp; &nbsp; &nbsp;if file then &nbsp; &nbsp; &nbsp; print("File Exists") &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; contents = file:read() or "[]" &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; newTable = json.decode(contents) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; print("File Contents:" .. contents) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; table.insert(newTable,dataTable) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; encodedJson = json.encode(newTable) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; file:write(encodedJson) &nbsp; &nbsp; &nbsp;else &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; print("File does not exist") &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; file = io.open(path, "w") &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; a = {} &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; table.insert(a,dataTable) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; file:write(json.encode(a)) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; print("Created new file \"SaveFile2.txt\" With source = " .. json.encode(a)) &nbsp; &nbsp; &nbsp;end &nbsp; &nbsp; file:close() end &nbsp; save({1,2,3})

now I ran this a few times and this is the output I got

22:11:53.293 File does not exist

22:11:53.303 Created new file “SaveFile2.txt” With source = [[1,2,3]]

22:12:12.569 File Exists

22:12:12.569 File Contents:[[1,2,3]]

22:12:16.626 File Exists

22:12:16.626 File Contents:[[1,2,3]][[1,2,3],[1,2,3]]

22:12:24.525 File Exists

22:12:24.525 File Contents:[[1,2,3]][[1,2,3],[1,2,3]][[1,2,3],[1,2,3]]

22:12:34.756 File Exists

22:12:34.756 File Contents:[[1,2,3]][[1,2,3],[1,2,3]][[1,2,3],[1,2,3]][[1,2,3],[1,2,3]]

22:12:37.902 File Exists

22:12:37.902 File Contents:[[1,2,3]][[1,2,3],[1,2,3]][[1,2,3],[1,2,3]][[1,2,3],[1,2,3]][[1,2,3],[1,2,3]]

22:12:40.739 File Exists

22:12:40.739 File Contents:[[1,2,3]][[1,2,3],[1,2,3]][[1,2,3],[1,2,3]][[1,2,3],[1,2,3]][[1,2,3],[1,2,3]][[1,2,3],[1,2,3]]

the end result of me running this should have looked like this

[[1,2,3],[1,2,3],[1,2,3],[1,2,3],[1,2,3],[1,2,3],[1,2,3]]

Scott_Harrison · June 21, 2016, 4:33am

I use this in my game

https://github.com/robmiracle/Simple-Table-Load-Save-Functions-for-Corona-SDK

thanks rob

nil · June 21, 2016, 5:10am

Thanks! This will work for android also right?

rob · June 21, 2016, 3:40pm

It works for all platforms except tvOS which doesn’t have a system.DocumentsDirectory to store things in.

nil · June 21, 2016, 8:05pm

I assume that people can open the saved json file and just edit it right?

Scott_Harrison · June 21, 2016, 8:11pm

You can encrypt the text in the file. I send you my version of the module when I get home. There is not much you can do to protect you files on android.

rob · June 21, 2016, 8:29pm

They would have to have a jailbroken or rooted device. They would have to go to effort to do so. A determined hacker will break any encryption you apply. But yes, the loadsave library writes in clear text and that file can be modified, if the person can get access to it.

Scott_Harrison · June 21, 2016, 8:36pm

Here is my code,

local M = {} local json = require("json") local \_defaultLocation = system.DocumentsDirectory local \_realDefaultLocation = \_defaultLocation local \_validLocations = { [system.DocumentsDirectory] = true, [system.CachesDirectory] = true, [system.TemporaryDirectory] = true } local enc1 = {86, 43, 70, 69, 14}; local function convert( chars, dist, inv ) return string.char( ( string.byte( chars ) - 32 + ( inv and -dist or dist ) ) % 95 + 32 ) end local crypt = function (str,k,inv) local enc= ""; for i=1,#str do if(#str-k[5] \>= i or not inv)then for inc=0,3 do if(i%4 == inc)then enc = enc .. convert(string.sub(str,i,i),k[inc+1],inv); break; end end end end if(not inv)then for i=1,k[5] do enc = enc .. string.char(math.random(32,126)); end end return enc; end 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) local tempString = crypt(contents,enc1,false) file:write( tempString ) 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" ) local tempString = crypt(contents,enc1,true) myTable = json.decode(tempString); 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

Of course I agree with rob. I would rather make it a little harder. This is the way do, I just want to stop the android user from going in do a quick modification. At the end of the day if someone wants to break into your house there is only so much you do while not having to unlock all the locks

nil · June 21, 2016, 8:59pm

Well if they don’t know the encryption code then It would be one hard time trying to decrypt a file

Scott_Harrison · June 21, 2016, 9:17pm

Hard time yes, impossible no

nil · June 21, 2016, 12:54am