Display results from CoreData using NSPredicate in Swift - ios

Question

I have the following code in my viewDidLoad()
fetchedResultsController = NSFetchedResultsController(fetchRequest: FetchRequest("Teams", key: "team_name"), managedObjectContext: managedObjectContext!, sectionNameKeyPath: nil, cacheName: nil)
fetchedResultsController?.delegate = self
fetchedResultsController?.performFetch(nil)
and this code in my TableView cellForRowAtIndex:
var cell = teamView.dequeueReusableCellWithIdentifier("team_cell", forIndexPath: indexPath) as! TeamCellSettings
if let cellContact = fetchedResultsController?.objectAtIndexPath(indexPath) as? Team {
//create cell here
}
return cell
I have read online on how to use NSPredicate, but I cannot seem to get it to work. My goal is to use a segmented control to switch between the results displayed in the UITableView based off of the contents of a row's attribute. So if my entity X had an attribute named A, A would store either a 1 or a 0, so basically I need the segmented control to switch between all the results containing a 1 in attribute A or a 0 in attribute A
My creative writing skills are not the best. Hope you can understand my goal. Thank you.

Answer 1

The predicate needs to be added to the fetch request, for example:
let request = NSFetchRequest(entityName: "Your entity name")
let predicate = NSPredicate(format: "A == %d", 1)
request.predicate = predicate
fetchedResultsController = NSFetchedResultsController(
fetchRequest: request,
managedObjectContext: managedObjectContext!,
sectionNameKeyPath: nil,
cacheName: nil)
What goes to the predicate depends on your goals. In a next step you will need to update the fetch request and reload the data as you change the selected item in the segmented control. In your IBAction that is called when the segmented control changes, get sender.selectedSegmentIndex and create the new predicate based on the index.
The code to refetch will look something like this:
Swift 2
fetchedResultsController.fetchRequest.predicate = NSPredicate(format: "A = %d", some_int_goes_here)
do {
try fetchedResultsController.performFetch()
}
catch let error as NSError {
NSLog("%#", error.localizedDescription)
}
catch {
fatalError()
}
tableView.reloadData()
If you do Swift 1.2, omit the error handling, of course, something like this:
fetchedResultsController.fetchRequest.predicate = NSPredicate(format: "A = %d", some_int_goes_here)
fetchedResultsController.performFetch()
tableView.reloadData()