rx_autoUpdater for ObservableArray-RxSwift

UITableView+ObservableArray_RxSwift.swift

import UIKit
import RxSwift
import ObservableArray_RxSwift

extension UITableView {
	public func rx_autoUpdater(source: Observable<ArrayChangeEvent>) -> Disposable {
		return source
			.scan((0, nil)) { (a: (Int, ArrayChangeEvent?), ev) in
				(a.0 + ev.insertedIndices.count - ev.deletedIndices.count, ev)
			}
			.observeOn(MainScheduler.instance)
			.subscribe(onNext: { sourceCount, event in
				guard let event = event else { return }

				let tableCount = self.numberOfRows(inSection: 0)
				guard tableCount + event.insertedIndices.count - event.deletedIndices.count == sourceCount else {
					self.reloadData()
					return
				}

				func toIndexSet(array: [Int]) -> [IndexPath] {
					return array.map { IndexPath(row: $0, section: 0) }
				}

				self.beginUpdates()
				self.insertRows(at: toIndexSet(array: event.insertedIndices), with: .automatic)
				self.deleteRows(at: toIndexSet(array: event.deletedIndices), with: .automatic)
				self.reloadRows(at: toIndexSet(array: event.updatedIndices), with: .automatic)
				self.endUpdates()
			})
	}
}