NsFetchedResultsController BatchUpdates

FetchBatchUpdates.swift

    private var sectionChanges: Array<Dictionary<NSFetchedResultsChangeType, Int>> = []
    private var itemChanges: Array<Dictionary<NSFetchedResultsChangeType, [IndexPath]>> = []

extension AwChatPresenterImplementation: NSFetchedResultsControllerDelegate {

    func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
        if controller == chatFetchResultController {
            sectionChanges = []
            itemChanges = []
        }
    }

    func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
        if controller == chatFetchResultController {
            awChatView.chatTableNode.performBatchUpdates({ [weak self] in
                guard let `self` = self else { return }
                for change in sectionChanges {
                    for (key, value) in change {
                        switch key {
                        case .insert:
                            self.awChatView.chatTableNode.insertSections(NSIndexSet(index: value) as IndexSet, with: .fade)
                        case .delete:
                            self.awChatView.chatTableNode.deleteSections(NSIndexSet(index: value) as IndexSet, with: .fade)
                        case .update:
                            self.awChatView.chatTableNode.reloadSections(NSIndexSet(index: value) as IndexSet, with: .fade)
                        case .move:
                            self.awChatView.chatTableNode.deleteSections(NSIndexSet(index: value) as IndexSet, with: .fade)
                            self.awChatView.chatTableNode.insertSections(NSIndexSet(index: value) as IndexSet, with: .fade)
                        }
                    }
                }
                
                for change in itemChanges {
                    for (key, value) in change {
                        switch key {
                        case .insert:
                            self.awChatView.chatTableNode.insertRows(at: value, with: .fade)
                        case .delete:
                            self.awChatView.chatTableNode.deleteRows(at: value, with: .fade)
                        case .update:
                            self.awChatView.chatTableNode.reloadRows(at: value, with: .fade)
                        case .move:
                            guard let atIndexPath = value[safe: 0], let toIndexPath = value[safe: 1] else { return }
                            self.awChatView.chatTableNode.moveRow(at: atIndexPath, to: toIndexPath)
                        }
                    }
                }
                
            }, completion: { _ in
                self.sectionChanges = []
                self.itemChanges = []
            })
        }
    }
    
    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) {
        
        let change = [type: sectionIndex]
        sectionChanges.append(change)
    }
    
    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
        
        var change: [NSFetchedResultsChangeType: [IndexPath]] = [:]

        switch type {

        case .insert:
            guard let newIndexPath = newIndexPath  else { return }
            change[type] = [newIndexPath]

        case .delete:
            guard let indexPath = indexPath else { return }
            change[type] = [indexPath]

        case .update:
            /* called when cell editing- not happening
             called when read,delivery status changes
             */

            guard let indexPath = indexPath else { return }
            change[type] = [indexPath]

        case .move:
            /* Move called when ever chat edited
             called when inserting new cell - bug
             */

            guard let deleteIndexPath = indexPath, let insertIndexPath = newIndexPath, deleteIndexPath == insertIndexPath else { return }
            change[type] = [deleteIndexPath, insertIndexPath]
        }
        itemChanges.append(change)
    }
}