CoreData : Fetch Multiple Entities using NSFetchedResultController

Question

I can fetch one entity and display the data in a tableview with single section using NSFetchedResultsController. But how to fetch two or more entities (no relation) using NSFetchedResultsController and display the data in different section?

I noticed that using core data, I can get number of section and number of row using NSFetchedResultsController. I set one entity in NSFetchedResultsController and it handles tableView very well including add and delete row.

func getFetchedResultController() - > NSFetchedResultsController {
  fetchedResultController = NSFetchedResultsController(fetchRequest: fetchRequest(), managedObjectContext: managedObjectContext!, sectionNameKeyPath: nil, cacheName: nil)
  fetchedResultController.delegate = self
  fetchedResultController.performFetch(nil)
  return fetchedResultController
}

func fetchRequest() - > NSFetchRequest {
  let fetchRequest = NSFetchRequest(entityName: "Fruits")
  let sortDescriptor = NSSortDescriptor(key: "desc", ascending: true)
  fetchRequest.sortDescriptors = [sortDescriptor]
  return fetchRequest
}

override func numberOfSectionsInTableView(tableView: UITableView) - > Int {
  let section = fetchedResultController.sections ? .count
  return section!
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) - > Int {
  if let s = fetchedResultController.sections as ? [NSFetchedResultsSectionInfo] {
    return s[section].numberOfObjects
  }
  return 0
}

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) - > UITableViewCell {
  var cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
  let fruit = fetchedResultController.objectAtIndexPath(indexPath) as Fruits
  cell.textLabel.text = fruit.desc
  return cell
}

But section always zero because it only uses one entity. Let say I want to show 2 entities/tables Fruits and Drinks (no relation), where should I put these entities in my code above? Can NSFetchedResultsController handles these entities in different section in tableView?

I found another way to do this, I read here but if NSFetchedResultController can do the same thing, I like to try. Is it possible and how? — Mat Yus
For info : If you have just started your project, you should try Realm : realm.io . Realm is very easy to use and abstract a lot of heavy code. Less code code for same performances. ;) — Pintouch

pbasdf pbasdf · Accepted Answer · 2014-11-22T00:52:30

Use two fetchedResultsControllers, say fruitFRC and drinksFRC, and then map the indexPath reported by those FRCs to the indexPath used by the tableView. For example, if fruit are to appear in section 0 of the tableView, you can just use the tableView indexPath to lookup in the fruitFRC to get the fruit details. But for drinks, in section 1 of the tableView, you need to create a new indexPath since the drinksFRC will be using section 0. (You can use indexPathForRow:inSection: method of NSIndexPath to create the new indexPath.)

Likewise, in numberOfRowsInSection, if the section is 0, return the number of objects in fruitFRC, and if the section is 1, return the number of objects in drinksFRC.

And so on...

CoreData : Fetch Multiple Entities using NSFetchedResultController

1 Answers