UITableViewController with NSFetchedResultsController boilerplate

fetched-results-controller.swift

//
//  MyViewController.swift
//
//  Created by Nate Armstrong on 4/15/15.
//  Copyright (c) 2015 Nate Armstrong. All rights reserved.
//

import UIKit
import CoreData

class MyViewController: UITableViewController {

  var context: NSManagedObjectContext!
  lazy var fetchedResultsController: NSFetchedResultsController = {
    let fetchRequest = NSFetchRequest()
    let entity = NSEntityDescription.entityForName("MyEntity", inManagedObjectContext: self.context)
    fetchRequest.entity = entity
    let sort = NSSortDescriptor(key: "updated_at", ascending: false)
    fetchRequest.sortDescriptors = [sort]
    let controller = NSFetchedResultsController(
      fetchRequest: fetchRequest,
      managedObjectContext: self.context,
      sectionNameKeyPath: nil,
      cacheName: "Root"
    )
    controller.delegate = self
    return controller
  }()

  override func viewDidLoad() {
    super.viewDidLoad()
    var error: NSError? = nil
    if !fetchedResultsController.performFetch(&error) {
      println("fetch error \(error)")
    }
  }

  override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
  }

  func configureCell(cell: UITableViewCell, atIndexPath indexPath: NSIndexPath) {
    cell.textLabel!.text = "Set text"
  }

}

// MARK: - Table view data source
extension ClientsViewController: UITableViewDataSource {

  override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    if let sectionInfo: AnyObject = fetchedResultsController.sections?[section] {
      return sectionInfo.numberOfObjects
    }
    return 0
  }

  override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("ClientCell", forIndexPath: indexPath) as! UITableViewCell
    configureCell(cell, atIndexPath: indexPath)
    return cell
  }

}

// MARK: - Fetched results controller delegate
extension ClientsViewController: NSFetchedResultsControllerDelegate {

  func controllerWillChangeContent(controller: NSFetchedResultsController) {
    tableView.beginUpdates()
  }

  func controllerDidChangeContent(controller: NSFetchedResultsController) {
    tableView.endUpdates()
  }

  func controller(controller: NSFetchedResultsController,
    didChangeObject anObject: AnyObject,
    atIndexPath indexPath: NSIndexPath?,
    forChangeType type: NSFetchedResultsChangeType,
    newIndexPath: NSIndexPath?) {
    switch type {
      case .Insert:
        tableView.insertRowsAtIndexPaths([newIndexPath!], withRowAnimation: .Fade)
      case .Delete:
        tableView.deleteRowsAtIndexPaths([indexPath!], withRowAnimation: .Fade)
      case .Update:
        self.configureCell(tableView.cellForRowAtIndexPath(indexPath!)!, atIndexPath: indexPath!)
      default:
        return
    }
  }

  func controller(controller: NSFetchedResultsController,
    didChangeSection sectionInfo: NSFetchedResultsSectionInfo,
    atIndex sectionIndex: Int,
    forChangeType type: NSFetchedResultsChangeType) {
    switch type {
      case .Insert:
        self.tableView.insertSections(NSIndexSet(index: sectionIndex), withRowAnimation: .Fade)
      case .Delete:
        self.tableView.deleteSections(NSIndexSet(index: sectionIndex), withRowAnimation: .Fade)
      default:
        return
    }
  }

}