When a user authenticate with Facebook in your app, where and how can you store data for other friends that also uses the app, can see?
For example. Imagine a simple blog-app. After you've authenticated you can submit a post to your blog. If any of your friends also uses the app, they can find your blog and see the post.
My question is this. Where do you save the blog post, and how do you retrieve it for the friend to see?
Do all Facebook users have a unique identifier which is accessible from the Facebook SDK? Could I for example save the blog post in a database with the bloggers Facebook ID? And when the friend requests to see any blog posts, could I access all hers friends IDs, and then loop through the database to see if any matches?
In that case, what would be the preferred way to set up the back-end server?
Even, is this the unique identifier ("id" field) I would use? http://graph.facebook.com/henrik.skogmo (me)
Facebook does not have any method for external data. It means you should save all of user's posts(if your app is a blog-app) on your own server. Also retrieving of friends' posts are must done on your server. After find user's friends via Facebook API and with the friend's IDs , you should get his posts from your server.
All of Facebook objects(user, app, page, etc.) have unique ID. In your graph API response, "id": "1042920928" is that. You can store user's friends list on your own server or load that whenever the client needs it. There's pros and cons so you should consider about whole structure.
Sorry for poor English, you can ask me if there's anything unclear.