CollectionViewController.swift

//
//  CollectionViewController.swift
//  Everest
//
//  Created by Caleb Davenport on 6/15/15.
//  Copyright (c) 2014-2015 Hodinkee. All rights reserved.
//

import UIKit

///
/// A `UICollectionViewController` class that properly implements
/// `flashScrollIndicators` and `clearsSelectionOnViewWillAppear`.
///
public class CollectionViewController: UICollectionViewController {

    // MARK: - Properties

    private var __clearsSelectionOnViewWillAppear = true

    public override var clearsSelectionOnViewWillAppear: Bool {
        get {
            return false
        }
        set {
            __clearsSelectionOnViewWillAppear = newValue
        }
    }


    // MARK: - UIViewController

    public override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)

        if __clearsSelectionOnViewWillAppear {
            if let indexPaths = collectionView?.indexPathsForSelectedItems() as? [NSIndexPath] {
                if let coordinator = transitionCoordinator() {
                    let animationBlock: (UIViewControllerTransitionCoordinatorContext!) -> () = { [weak self] _ in
                        self?.deselectItemsAtIndexPaths(indexPaths, animated: animated)
                    }
                    let completionBlock: (UIViewControllerTransitionCoordinatorContext!) -> () = { [weak self] context in
                        if context.isCancelled() {
                            self?.selectItemsAtIndexPaths(indexPaths, animated: false)
                        }
                    }
                    coordinator.animateAlongsideTransition(animationBlock, completion: completionBlock)
                }
                else {
                    deselectItemsAtIndexPaths(indexPaths, animated: animated)
                }
            }
        }
    }
    
    public override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        collectionView?.flashScrollIndicators()
    }


    // MARK: - Private

    private func deselectItemsAtIndexPaths(indexPaths: [NSIndexPath], animated: Bool) {
        for indexPath in indexPaths {
            collectionView?.deselectItemAtIndexPath(indexPath, animated: animated)
        }
    }

    private func selectItemsAtIndexPaths(indexPaths: [NSIndexPath], animated: Bool) {
        for indexPath in indexPaths {
            collectionView?.selectItemAtIndexPath(indexPath, animated: animated, scrollPosition: .None)
        }
    }
}

TableViewController.swift

//
//  TableViewController.swift
//  Everest
//
//  Created by Caleb Davenport on 9/16/15.
//  Copyright (c) 2014-2015 Hodinkee. All rights reserved.
//

import UIKit

public class TableViewController: UITableViewController {

    // MARK: - Properties

    private var __clearsSelectionOnViewWillAppear = true

    public override var clearsSelectionOnViewWillAppear: Bool {
        get {
            return false
        }
        set {
            __clearsSelectionOnViewWillAppear = newValue
        }
    }


    // MARK: - UIViewController

    public override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)

        if __clearsSelectionOnViewWillAppear {
            if let indexPaths = tableView?.indexPathsForSelectedRows() as? [NSIndexPath] {
                if let coordinator = transitionCoordinator() {
                    let animationBlock: (UIViewControllerTransitionCoordinatorContext!) -> () = { [weak self] _ in
                        self?.deselectItemsAtIndexPaths(indexPaths, animated: animated)
                    }
                    let completionBlock: (UIViewControllerTransitionCoordinatorContext!) -> () = { [weak self] context in
                        if context.isCancelled() {
                            self?.selectItemsAtIndexPaths(indexPaths, animated: false)
                        }
                    }
                    coordinator.animateAlongsideTransition(animationBlock, completion: completionBlock)
                }
                else {
                    deselectItemsAtIndexPaths(indexPaths, animated: animated)
                }
            }
        }
    }


    // MARK: - Private

    private func deselectItemsAtIndexPaths(indexPaths: [NSIndexPath], animated: Bool) {
        for indexPath in indexPaths {
            tableView?.deselectRowAtIndexPath(indexPath, animated: animated)
        }
    }

    private func selectItemsAtIndexPaths(indexPaths: [NSIndexPath], animated: Bool) {
        for indexPath in indexPaths {
            tableView?.selectRowAtIndexPath(indexPath, animated: animated, scrollPosition: .None)
        }
    }
}