Many-to-Many entities and NSPopUpButton

Question

all.

Entities:

[Library {title}] <-->> [Book {title}] <<-->> [Author {name}]

Controllers:

NSArrayController [Library] => {Entity: Library}
NSArrayController [Book] => {Entity: Book, ContentSet: Library, books}
NSArrayController [Author] => {Entity: Author, ContentSet: Book, authors}
NSArrayController [Authors] => {Entity: Author}

Form:

[ NSPopUpButton *]
[ NSTableView **]
[ add ] [ remove ]

* button get content from NSArrayController [Author w/o contentset option]

** table get content from another NSArrayController [Author with contentset option set as Library.books]

Question:

how i can add Author into Book.authors from Author entity? (Use previous authors for any book)

Answer 1

1) set PopUpButton property

   {
     Content: NSArrayController [Authors], ArrangedObjects
     Content Values: NSArrayController [Authors], ArrangedObjects, name
     Selected Index: NSArrayController [Authors], selectionIndex
   }

2) add

@property (assign) IBOutlet *authorsController, *bookController; 

and link it with NSArrayControllers

3) add this code and link with button:

- (IBAction)insertSelectedItem:(id)sender
{
    MOAuthor *author = self.authorsController.content[self.authorsController.selectionIndex]; // get current (selected) author

    MOBook *book = self.bookController.content[self.bookController.selectionIndex]; // get current guide

    [book addAuthorsObject:author]; // add step into guide

    NSError *err = nil;

    [book.managedObjectContext save:&err]; // save all
}

MOBook, MOAuthor - ManagedObject class created from Entity