Saving and loading data files

SinisterSoft · April 2017

A nice way to save load data is by using json, here is one way to do it.

First, somewhere early in your code load the json library...

pcall(function() require "json" end)

Then here is a save routine for a sample table:

function save()
	if json then
		local savedata={}
		savedata["highscore"]=hiscore
		local file=io.open("|D|data.txt","w+")
		if file then
			pcall(function() file:write(json.encode(savedata)) end)
			file:close()
		end
	end
end

Just copy the variables you need saving into the temporary savedata table.

Alternatively you could have the savedata table outside the function and use it throughout your game.

Here is a load routine to load the table:
function load()
	if json then
		local file=io.open("|D|data.txt","r")
		if file then
			local originaldata=file:read()
			file:close()
			if originaldata then
				local decoded=json.decode(originaldata)
				if decoded then
					hiscore=tonumber(decoded["hiscore"])
				end
			end
		end
	end
	if hiscore==nil then hiscore=0 end
end

Notice the check at the end to set valid values if for any reason the results are nil.

HubertRonald · April 2017

Notice the check at the end to set valid values if for any reason the results are nil.

Oh! yes @SinisterSoft Sometimes also headaches come when a formula (percentage of advance or other method) of 0/0 and produces NaN See more details here: ...Json: Error reading 'null' and you try save it with json

MoKaLux · April 2024

oh this is SinisterSoft who came up with this great solution, I use it everyday

thank you mister SinisterSoft

PS: for ref

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