How to load json file from arbitrary folder inside project? - lua

Question

How to load json file from arbitrary folder inside project ?
I have data folder and inside file user_data.json, but system.DocumentsDirectory points to another ( I have copied from net, I am pretty new to lua and corona)
function custom_load( strFilename )
local path = system.pathForFile( strFilename, system.DocumentsDirectory )
local file = io.open( path, "r" )
if file then
local content = file:read( "*a" )
io.close( file )
return contents
else
return ''
end
end

Answer 1

Your file has to exist before you can read it. Perhaps a brief description of the Corona SDK folder structure will help you understand what's going on.
All apps, regardless of iOS, Android or Corona while running in the simulator are made of up an "Application Bundle". In iOS terms, this is the .app file that Corona SDK produces. In Android, it's the .apk file. The files in the folder with your main.lua and any folders you create there are part of this app bundle. For security purposes, this folder is "Read Only" to your app. Corona SDK allows you to reference files in this folder as system.ResourceDirectory.
Once the app is created and running on the device, Three other folders are created in your App's Sandbox. This is an area that only your app can access. These are:
system.DocumentsDirectory, a readable and writable folder to store things you want to keep around with your app. This is where you would save settings files, files that your users create with your app and so on.
system.TemporaryDirectory, a readable and writeable folder to store things you don't expect to be there. It's where you can download files to that you intend to throw away.
Apple's iOS has a 3rd folder that Corona calls system.CachesDirectory which like system.TemporaryDirectory has not guarantees on now long files that are stored there will last, but the intent from Apple is if you can download it from the net and it gets deleted, you can always download it again. On Android, system.CachesDirectory and system.TemporaryDirectory are the same folders.
Since the assumption is the app is the only thing that can write to it's sandbox, files in system.DocumentsDirectory have to be created by the app. You can't just put a file there (okay there are ways in particular on the simulator, it's just a folder on your Mac or PC if you know where to look, but that's not realistic of a user loading your app) so your app has to create the file in system.DocumentsDirectory.
If the file has not been created, then trying to use io.open() in "read" mode ( the "r" ) to open a file will return nil because the file does not exist.

Answer 2

Dont worry its very simply , just refer this code you will automatically code after reading this.
https://github.com/robmiracle/Simple-Table-Load-Save-Functions-for-Corona-SDK/blob/master/main.lua

Answer 3

In pathForFile use
local path = system.pathForFile( "data/user_data.json", system.ResourceDirectory)