Is it possible for an iOS app to tell if the user has set it to only me, public or friends only?
For example, the basic setting was set to public.
The iOS app would now bring up a post to wall dialog, letting the user add their own text, but on the computer, the user has changed the privacy setting of the app to Me Only or Friends.
Can the App test for the current privacy setting before the post is made?
It is possible to check the setting in which a user has shared the post using the Facebook Graph API. But you will need READ STREAM permission from the Facebook API. Here is the reference to the Graph API.
Basically you have to have READ STREAM permission. You have to share to Facebook and the success callback will give you a post id. You can use this post id to get all the details related to this post, including the audience (Only Me/Friends/Public).