Reference (Old Docs)
FBSDKMessengerURLHandlerReplyContext
A more recent version of this class is available. Check out the latest version.

This object represents a user tapping reply from a message in Messenger. Passing this context into a share method will trigger the reply flow

Superclass:FBSDKMessengerContext
Declared in:FBSDKMessengerURLHandlerReplyContext.h
Properties
metadata

Additional information that was passed along with the original media that was replied to

@property (nonatomic, copy, readonly) NSString *metadata;
Discussion:

If content shared to Messenger incuded metadata and the user replied to that message, that metadata is passed along with the reply back to the app. If no metadata was included this is nil

Declared In: FBSDKMessengerURLHandlerReplyContext.h
userIDs

The user IDs of the other participants on the thread.

@property (nonatomic, copy, readonly) NSSet *userIDs;
Discussion:

User IDs can be used with the Facebook SDK and Graph API (https://developers.facebook.com/docs/graph-api) to query names, photos, and other data. This will only contain IDs of users that have also logged into your app via their Facebook account.

Declared In: FBSDKMessengerURLHandlerReplyContext.h