SearchBar & Display in table view with Coredata using Swift? - swift

Question

I am new to iOS development and am in my second app with Swift. I am unable to incorporate SearchBar & Display search in my Table view controller.
There are 2 views in my app. First View generates an Array of fruits. Output of First View: [Apple, Orange, Banana, Pears]. Then [Pomegranate, Pears, Watermelon, Muskmelon] and so on. One array at a time.
Each array of fruits is stored in core-data using NSFetchedResultsController to be displayed in a tableviewcontroller.
My Coredata layout:
import UIKit
import CoreData
#objc(Fruits)
class Fruits: NSManagedObject {
#NSManaged var date: String
#NSManaged var fruit: String
}
My Second View displays the list of fruits. Now I have added a Search Bar & Display on top on the table view. But I am unable to make it work.
Protocols used:
class HistoryTableViewController: UITableViewController, NSFetchedResultsControllerDelegate{
Variables declared:
let managedObjectContext: NSManagedObjectContext? = (UIApplication.sharedApplication().delegate as? AppDelegate)?.managedObjectContext
var fetchedResultsController: NSFetchedResultsController?
var fetchRequest = NSFetchRequest(entityName: "Fruits")
There are two outlets in my class:
#IBOutlet weak var searchBar: UISearchBar! // the Search Bar & Display
#IBOutlet var tblHistory: UITableView! = nil // Table View
Data population for table view:
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return fetchedResultsController?.sections?.count ?? 0
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int
{
return fetchedResultsController?.sections?[section].numberOfObjects ?? 0
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: (NSIndexPath!)) -> UITableViewCell
{
let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath) as UITableViewCell
if let cellFruit = fetchedResultsController?.objectAtIndexPath(indexPath) as? Fruits
{
cell.textLabel?.text = cellFruit.fruit
cell.detailTextLabel?.text = cellFruit.date
}
return cell
}
// Override to support conditional editing of the table view.
override func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool {
// Return false if you do not want the specified item to be editable.
return true
}
//MARK: NSFetchedResultsController Delegate Functions
func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {
switch type {
case NSFetchedResultsChangeType.Insert:
tableView.insertSections(NSIndexSet(index: sectionIndex), withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Delete:
tableView.deleteSections(NSIndexSet(index: sectionIndex), withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Move:
break
case NSFetchedResultsChangeType.Update:
break
default:
break
}
}
override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
//Delete object from entity, remove from list
if editingStyle == .Delete {
}
switch editingStyle {
case .Delete:
managedObjectContext?.deleteObject(fetchedResultsController?.objectAtIndexPath(indexPath) as! Fruits)
do {
try managedObjectContext?.save()
}catch{}
print("Fruit set deleted successfully.")
case .Insert:
break
case .None:
break
}
}
func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
switch type {
case NSFetchedResultsChangeType.Insert:
tableView.insertRowsAtIndexPaths(NSArray(object: newIndexPath!) as! [NSIndexPath], withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Delete:
tableView.deleteRowsAtIndexPaths(NSArray(object: indexPath!) as! [NSIndexPath], withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Move:
tableView.deleteRowsAtIndexPaths(NSArray(object: indexPath!) as! [NSIndexPath], withRowAnimation: UITableViewRowAnimation.Fade)
tableView.insertRowsAtIndexPaths(NSArray(object: newIndexPath!) as! [NSIndexPath], withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Update:
tableView.cellForRowAtIndexPath(indexPath!)
break
default:
break
}
}
func controllerWillChangeContent(controller: NSFetchedResultsController) {
tableView.beginUpdates()
}
func controllerDidChangeContent(controller: NSFetchedResultsController) {
tableView.endUpdates()
}
How do I Search any fruit from coredata and filter on the view?
Which delegate function should be used for the search bar & display functionality in Swift coding?
Any help on a concept I might have missed somewhere in here would be appreciated! Thanks.
Update: as Daniel Eggert suggested I am trying to use predicate for the Search Controller functionality, but the Predicate always gives a nil. What am I missing???
Variables declared in class:
var results: NSArray = []
var searchPredicate: NSPredicate?
var searchController: UISearchController!
Predicate Functions:
//Search Functionality
func updateSearchResultsForSearchController(searchController: UISearchController)
{
let searchText = self.searchController?.searchBar.text
if let searchText = searchText {
searchPredicate = NSPredicate(format: "fruit contains[cd] %#", searchText)
results = (self.fetchedResultsController!.fetchedObjects?.filter() {
return self.searchPredicate!.evaluateWithObject($0)
} as! [Fruits]?)!
self.tableView.reloadData()
}
}
// Called when text changes (including clear)
func searchBar(searchBar: UISearchBar, textDidChange searchText: String)
{
if !searchText.isEmpty
{
var predicate: NSPredicate = NSPredicate()
predicate = NSPredicate(format: "fruit contains [cd] %#", searchText)
let sortDescriptor = NSSortDescriptor(key: "date", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
fetchedResultsController?.fetchRequest.predicate? = predicate
print(fetchedResultsController?.fetchRequest.predicate) // this is always nil. Why????????????
do {
try fetchedResultsController?.performFetch()
}catch{}
print("results array: \(results)") // this array should have values of the table view, but is empty. Why ?????????????????
fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: managedObjectContext!,
sectionNameKeyPath: "fruit", cacheName: nil)
fetchedResultsController?.delegate = self
tableView.reloadData()
}
}

Answer 1

You want to set a predicate on you fetched results controller.
Once you've changed the fetch request on the fetched results controller you need to call performFetch() to have it refetch its data. Then call reloadData() on the table view.
Text search for non-trivial examples can be tricky to do right, though, due to how languages, locales, and Unicode interact. I'd recommend the Text chapter of my book: https://www.objc.io/books/core-data/

Answer 2

If you want to implement searchable tableView? You're must must use UISearchResultsUpdating protocol method instead of the UISearchBarDelegate protocol method called searchBar:textDidChange. You can use searchBar:textDidChange method when UISearchResultsUpdating protocol method is not available! Both classes are useful and powerful. And easy to implement