Saving file information is used in many aspects of game development. We use it to save high scores and game settings, such as sound on/off, locking/unlocking levels, and so on. It is not necessary to have these features, but as they are good to have, maybe you'd like to include them in your applications.
In Corona SDK, applications are sandboxed; this means that your files (application images, data, and preferences) are stored in a location that no other application can access. Your files will reside in an app-specific directory for documents, resources, or temporary files. This restriction is related to the files on your device, not when you are coding on your Mac or PC.
We'll be using the BeebeGames class created by Jonathan Beebe. It provides many easy and useful functions to use for games. Some of the notable functions included incorporate a simple way of saving and loading data that we'll be able add into our game. More documentation on the BeebeGames class can be found in the Chapter 8 folder.
You can also refer to https://github.com/lewisNotestine/luaCorona/blob/master/justATest/code/beebegames.lua to track updates on the class.
You can take a look at other methods relating to animation, transitions, timers, and so on if you would like to use them for future use. For now, we'll focus on the methods we can use to easily save and load values for our game.
Here is an example of saving and loading values:
-- Public Method: saveValue() --> save single-line file (replace contents)
function saveValue( strFilename, strValue )
-- will save specified value to specified file
local theFile = strFilename
local theValue = strValue
local path = system.pathForFile( theFile, system.DocumentsDirectory)
-- io.open opens a file at path. returns nil if no file found
-- "w+": update mode, all previous data is erased
local file = io.open( path, "w+" )
if file then
-- write game score to the text file
file:write( theValue )
io.close( file )
end
end
-- Public Method: loadValue() --> load single-line file and store it into variable
function loadValue( strFilename )
-- will load specified file, or create new file if it doesn't exist
local theFile = strFilename
local path = system.pathForFile( theFile, system.DocumentsDirectory)
-- io.open opens a file at path. returns nil if no file found
-- "r": read mode
local file = io.open( path, "r" )
if file then
-- read all contents of file into a string
-- "*a": reads the whole file, starting at the current position
local contents = file:read( "*a" )
io.close( file )
return contents
else
-- create file b/c it doesn't exist yet
-- "w": write mode
file = io.open( path, "w" )
file:write( "0" )
io.close( file )
return "0"
end
endThe paths to these files are unique to your application. To create file paths, you can use the system.pathForFile function. This function generates an absolute path to the icon file for your application, using the application's resource directory as the base directory for Icon.png:
local path = system.pathForFile( "Icon.png", system.ResourceDirectory)
In general, your files must reside in one of the three possible base directories:
system.DocumentsDirectory: This should be used for files that need to persist between application sessions.system.TemporaryDirectory: This is a temporary directory. Files written to this directory are not guaranteed to exist in subsequent application sessions. They may or may not exist.system.ResourceDirectory: This is the directory where all application assets exist. Note that you should never create, modify, or add files to this directory.More information on files can be found at http://docs.coronalabs.com/api/library/system/index.html.