iPhone: NSFetchedResultsController for each Entity?

I have three entities with one-to-many relationships (Book <--->> Page <--->> Text) I want to use one table view to present Book.titles, one table view for Page.no and one view to show the Text when clicking on a Page.no.

Do I need to setup up a fetchedResultsController for each entity or can I get access to a Text object usin开发者_运维百科g the Book entity - Book.pages... etc?

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If I understand your question correctly, you only need one fetched results controller and CoreData will do the rest.

So, you fill an NSFetchedResultsController with all the books you want to display and present them with a UITableViewController subclass. Then when the user selects one, you pass this book on to another UITableViewController subclass which uses book.pages to get and display all the pages in that book. This idea is then repeated to show the text entities.

HTH

PS - If you aren't already, you may find it useful to use xCode's Managed Object Class generator to ensure book.pages and pages.texts are correctly set up. To use this, open your .xcdatamodel file, highlight an entity and choose File->New File and choose Managed Object Class and then follow the steps.

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You can access all objects via the relationships but depending on how complex your tableviews are, it may get tricky to manage the datasource methods. It's doable though!

For instance, if you decide to fetch the books, provided you have a reference to the instance you get all pages and put them in an Array with:

Book *bookItem = [self.frc objectAtIndexPath:indexPath];
NSArray *dataSource = [[book objectForKey:@"pages"] allObjets];

Another option is to create an abstract class and make it a parent of all 3 entities, then fetch using this class which will give you an array of all books, pages and text. From there you can test for the class and populate the tables accordingly.