LUA: how do you save someones progress? - lua

Question

lets say you have a script like this
print("you've been here for the first time.")
print("you're here for second or more time")
how would you make it so once a person runs the script once, instead of repeating the whole script it just goes to the second print right away?

Answer 1

You basically need to:
Save the state of the program when the program ends
Restore the state of the program when the program starts
There are several ways to store the state, the simplest way would be to create a file and store the state inside. One could also use the Windows Registry, a database, a remote server, etc.
A simple example:
function FileExists (Filename)
local File = io.open(Filename, "r")
if File then
File:close()
end
return File
end
function CreateFile (Filename)
local File = io.open(Filename, "w")
if File then
File:close()
end
end
ProgramStateFile = "program-state.txt"
if not FileExists(ProgramStateFile) then
print("you've been here for the first time.")
else
print("you're here for second or more time")
end
CreateFile(ProgramStateFile)
In this example, the state is only the existence of the state file. Obviously, you can extend this example by writing additional information inside the file.
function ReadState (Filename)
local File = io.open(Filename, "r")
local State
if File then
State = File:read("a")
File:close()
end
return State
end
function WriteState (Filename, State)
local File = io.open(Filename, "w")
if File then
File:write(State)
File:close()
end
end
ProgramStateFile = "program-state.txt"
if ReadState(ProgramStateFile) ~= "PROGRAM-FINISHED" then
print("you've been here for the first time.")
else
print("you're here for second or more time")
end
WriteState(ProgramStateFile, "PROGRAM-FINISHED")
Finally, please note that there are many formats already existing to store the states: INI file, XML, JSON, etc. For Lua, you could also use a serialization library in order to store a Lua table directly inside a file. I would personally recommend the binser library.