automatically sync collection view with.a fetch result controller.

FetchResutlControllerWithCollectionView.swift

//
//  FetchResultsControllerWithCollectionView.swift
//  CoreStore
//
//  Created by Arash Kashi on 2/23/17.
//  Copyright © 2017 Arash K. All rights reserved.
//
import Foundation
import CoreData
import UIKit



class FetchResultsControllerWithCollectionView: NSObject, NSFetchedResultsControllerDelegate {
    
    var collectionView: UICollectionView!
    var fetchResultController: NSFetchedResultsController<NSManagedObject>
    
    init(fetchResultController: NSFetchedResultsController<NSManagedObject>
        , collectionView: UICollectionView) {
        
        self.collectionView = collectionView
        self.fetchResultController = fetchResultController
        
        super.init()
        fetchResultController.delegate = self
        
        try? fetchResultController.performFetch()
        collectionView.reloadData()
    }
    
    var blockOperations: [BlockOperation] = []
    
    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
        
        if type == NSFetchedResultsChangeType.insert {
          NSLog("Insert Object: \(String(describing: newIndexPath))")
            
            blockOperations.append(
                BlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.insertItems(at: [newIndexPath!])
                    }
                })
            )
        }
        else if type == NSFetchedResultsChangeType.update {
            NSLog("Update Object: \(String(describing: newIndexPath))")
            blockOperations.append(
                BlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.reloadItems(at: [indexPath!])
                    }
                })
            )
        }
        else if type == NSFetchedResultsChangeType.move {
            NSLog("Move Object: \(String(describing: newIndexPath))")
            
            blockOperations.append(
                BlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.moveItem(at: indexPath!, to: newIndexPath!)
                    }
                })
            )
        }
        else if type == NSFetchedResultsChangeType.delete {
            NSLog("Delete Object: \(String(describing: newIndexPath))")
            
            blockOperations.append(
                BlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.deleteItems(at: [indexPath!])
                    }
                })
            )
        }
    }
    
    public func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) {
        
        
        if type == NSFetchedResultsChangeType.insert {
            NSLog("Insert Section: \(sectionIndex)")
            
            blockOperations.append(
                BlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.insertSections(NSIndexSet(index: sectionIndex) as IndexSet)
                    }
                })
            )
        }
        else if type == NSFetchedResultsChangeType.update {
            NSLog("Update Section: \(sectionIndex)")
            blockOperations.append(
                BlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.reloadSections(NSIndexSet(index: sectionIndex) as IndexSet)
                    }
                })
            )
        }
        else if type == NSFetchedResultsChangeType.delete {
            NSLog("Delete Section: \(sectionIndex)")
            
            blockOperations.append(
                BlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.deleteSections(NSIndexSet(index: sectionIndex) as IndexSet)
                    }
                })
            )
        }
    }
    
    func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
        collectionView!.performBatchUpdates({ () -> Void in
            for operation: BlockOperation in self.blockOperations {
                operation.start()
            }
        }, completion: { (finished) -> Void in
            self.blockOperations.removeAll(keepingCapacity: false)
        })
    }
    
    deinit {
        for operation: BlockOperation in blockOperations {
            operation.cancel()
        }
        
        blockOperations.removeAll(keepingCapacity: false)
    }
}