How can I invite other Facebook users to my iPhone app with extras?

If I want to get information about a user's friends in an iPhone app that integrates Facebook SDK, how do I ask the user to invite their friends to use the app and once the friend accepts the invite开发者_StackOverflow中文版 to ask those people to provide the "user_relationship_details" permission?

In other words, what code or methods do I use?

There currently is no support for this through the iOS SDK or any API call. The one thing you could do is load an HTML page in a frame or link to a page that allows the user to use the Request-Form FBML item. You can see more on that here: http://developers.facebook.com/docs/reference/fbml/request-form