When making your games it may be necessary to have content downloaded from a web server, for things like IAP, daily content, user levels, etc... However, if you try to store these files in the standard working_directly location then your game will be rejected during store submission with the error:
App submission failed: Apps must follow the iOS data storage guidelines
This happens because the working_directory in GameMaker games points to the following path by default:
This is only to be used for documents that the user has created or may want to back up to iCloud such as save files and screenshots. Web server downloaded content must be saved in a different directory for the game to pass store submission, something like:
To save to this location then you have to set the save location to:
working_directory + "/../Library/Caches/"
var save_location = working_directory+'/../Library/Caches/myDownload.file';