I have two applications named, for example, App_A and App_B. I have UIActivityViewController to share single or group of files:
NSArray *itemsToShare = [self getItemsToShare]; // returns list with NSUrl objects
UIActivityViewController *activityViewController = [[UIActivityViewController alloc] initWithActivityItems:itemsToShare applicationActivities:nil];
// presenting controller
There are different ways to communicate info to another app. In your case, you have decided to use
application:openURL:sourceApplication:annotation:. In that case, yes, this is only for handing one object to other app. It is intended for letting the user copy a file from the current app to the other app's inbox.