Topic: where to define global folder address?

i have some photo functionality where if the user deletes the photo, i also delete the folder(using acts as attachment). on my development box, i need to put the full path to the folder that needs to be deleted. however, on my other box, i can use ../somefolder as the folders address to delete the folder, whereas on the dev box i need to specify /var/www/railsapp/public/folder to delete.

is it possible to assign this address so i dont have to modify it in different environments?