Core Data: Showing NSFetchRequestResult Search Results with UITableView - swift

Question

I've been playing Core Data for the past several days. I'm fetching data with NSFetchedResultsController. My entity has such attributes as age (Int), firstName (String), lastName (String), uuid (String). I am able to insert a new record to the database. I am able to delete a record. I am also able to edit a record. What I cannot do is to show a search result with the table.
class HomeViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
// MARK: - Instance variables
private let persistentContainer = NSPersistentContainer(name: "Profiles") // core data model file (.xcdatamodeld)
var managedObjectContext: NSManagedObjectContext?
// MARK: - IBOutlets
#IBOutlet weak var tableView: UITableView!
#IBOutlet weak var searchButton: UIButton!
// MARK: - IBActions
#IBAction func searchTapped(_ sender: UIButton) {
searchRecords()
}
// MARK: - Life cycle
override func viewDidLoad() {
super.viewDidLoad()
// loading persistentContainer //
persistentContainer.loadPersistentStores { (persistentStoreDescription, error) in
if let error = error {
print("Unable to Load Persistent Store")
print("\(error), \(error.localizedDescription)")
} else {
do {
try self.fetchedResultsController.performFetch()
} catch {
let fetchError = error as NSError
print("Unable to Perform Fetch Request")
print("\(fetchError), \(fetchError.localizedDescription)")
}
}
}
}
// MARK: - Life cycle
// MARK: - fetchedResultsController(controller with the entity)
fileprivate lazy var fetchedResultsController: NSFetchedResultsController<Person> = {
// Create Fetch Request with Entity
let fetchRequest: NSFetchRequest<Person> = Person.fetchRequest()
// Configure Fetch Request
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "lastName", ascending: true)]
// Create Fetched Results Controller
let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.persistentContainer.viewContext, sectionNameKeyPath: nil, cacheName: nil)
// Configure Fetched Results Controller
fetchedResultsController.delegate = self
return fetchedResultsController
}()
// MARK: - fetchedResultsController
// MARK: - TableView
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
guard let people = fetchedResultsController.fetchedObjects else { return 0 }
return people.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! ProfileTableViewCell
let person = fetchedResultsController.object(at: indexPath)
// Configure Cell
cell.firstLabel.text = person.firstName
cell.lastLabel.text = person.lastName
cell.ageLabel.text = String(person.age)
return cell
}
// MARK: - TableView
// MARK: - Showing search result
func searchRecords() {
let context = self.persistentContainer.viewContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Person")
let predicate = NSPredicate(format: "firstName CONTAINS[c] %#", "Sandra")
fetchRequest.predicate = predicate
do {
try fetchedResultsController.performFetch()
/*
let result = try context.fetch(fetchRequest)
if (result.count > 0) {
print(result.count)
}
*/
} catch {
print("bad")
}
}
// MARK: - Showing search result
}
extension HomeViewController: NSFetchedResultsControllerDelegate {
func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
tableView.beginUpdates()
}
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
tableView.endUpdates()
}
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
switch (type) {
case .insert:
if let indexPath = newIndexPath {
tableView.insertRows(at: [indexPath], with: .fade)
}
break;
case .delete:
if let indexPath = indexPath {
tableView.deleteRows(at: [indexPath], with: .fade)
}
break;
case .update:
if let indexPath = indexPath {
tableView.reloadRows(at: [indexPath], with: .automatic)
}
break;
default:
tableView.reloadData()
}
}
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) {
}
}
If I run searchRecords(), result.count will correctly return the number of records. But the table stays the same. So how can I show my search result with the table? Thanks.

Answer 1

Replace your tableview datasource with
// MARK: - Table View
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return self.fetchedResultsController.sections?.count ?? 0
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
let sectionInfo = self.fetchedResultsController.sections![section]
return sectionInfo.numberOfObjects
}
Hope it is helpful

Answer 2

You've got more experience than I do, but the last time I used CoreData and a collectionView I needed to force cast the result like this:
do {
return try context.fetch(request) as? [Friend]
} catch let err {
print(err)
}
Then I was able to pull the info to the table more easily.