iCloud Document Storage with UIDocument - Beginning iOS Cloud and Database Development - page 74

The final step is to go back and adjust the FriendsCollectionViewController . Open the FriendsColl
ectionViewController.h file and add the import for the FriendDetailViewController.h file.

#import "FriendDetailViewController.h"

We also need to subscribe to the FriendDetailViewControllerDelegate Protocol. Your interface line
should now look like this:

@interface FriendsCollectionViewController : UICollectionViewController <UICollectionViewDataSource,
UICollectionViewDelegate, EntryCollectionViewCellDelegate, UIAlertViewDelegate,
FriendDetailViewControllerDelegate>

Now we need to add the delegate method detailViewControllerDidClose: . The only thing
we are doing right now is telling our navigation controller to go to the root controller by calling
popToRootViewControllerAnimated :. We will do more with this method later.

#pragma mark - FriendDetailViewControllerDelegate Methods
-(void)detailViewControllerDidClose:(FriendDetailViewController *)detailViewController {
[self.navigationController popToRootViewControllerAnimated:YES];
}

Finally, let's update our prepareForSegue:sender method so that it looks like this:

#pragma mark - Navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:@"ToFriendDetails"]){
[[segue destinationViewController] setDelegate:self];
[[segue destinationViewController] setShouldStartEditing:_shouldStartEditing];
}

}

Here we are just assigning our self as the delegate for the FriendDetailViewController and sending
our property _shouldStartEditing . Remember this is the Boolean value that determines if we
launch the view in edit more or if we are just viewing.

Go ahead and build and run the app. You should be able to add new Friends, delete them if you
long press on them too. You can select an image in the detail view and it will show up in that view.
None of this is being saved yet, but it lays the foundation for us to concentrate solely on integrating
UIDocument .

UIDocument
UIDocument is an abstract base class that handles the managing of data and documents.
Subclassing UIDocument gives you a lot of things right of the box such as:
Asynchronous reading and writing of data on a background queue. 

 Coordinated reading and writing of document files already integrated

with iCloud.