UIActivityViewController that adds an Open In option

Activity+OpenIn.swift

//
//  ViewController.swift
//  ShareTest
//
//  Created by A J LEVINGS on 24/07/2016.
//  Copyright © 2016 Gylphi. All rights reserved.
//

import UIKit
let UIActivityTypeOpenIn = "OpenIn"

class OpenIn: UIActivity {
    var docController: UIDocumentInteractionController!
    weak var barButton: UIBarButtonItem!
    
    // it's necessary to know which button the UIActivityViewController originated from
    init(barButton barB: UIBarButtonItem) {
        self.barButton = barB
    }
    // this provides a way of excluding the activity if we wish
    override func activityType() -> String? {
        return UIActivityTypeOpenIn
    }
    // provides title within popover
    override func activityTitle() -> String? {
        // your activity title here
        return "Open In..."
    }
    // in real use you would provide image here at required size (see class reference)
    override func activityImage() -> UIImage? {
        // return your icon image here, for simplicity I've used nil
        return nil
    }
    // specify whether Action or Share (default is Action)
    override class func activityCategory() -> UIActivityCategory {
        // ,Share places the option on the top row
        return .Share
    }
    // confirm the action can be performed
    override func canPerformWithActivityItems(activityItems: [AnyObject]) -> Bool {
        for a in activityItems {
            if a is NSURL  {
                return true
            }
        }
        return false
    }
    // prepare for the activity
    override func prepareWithActivityItems(activityItems: [AnyObject]) {
        for a in activityItems {
            if let url = a as? NSURL  {
                docController = UIDocumentInteractionController(URL: url)
            }
        }
    }
    // perform the activity
    override func performActivity() {
        docController.presentOpenInMenuFromBarButtonItem(barButton, animated: true)
    }
}

class ViewController: UIViewController {
    
    // UIDocumentInteractionController instance is a class property
    var activityController: UIActivityViewController!
    @IBOutlet weak var shareButton: UIBarButtonItem!
    // called when bar button item is pressed
    @IBAction func shareStuff(sender: AnyObject) {
        if let barButton = sender as? UIBarButtonItem {
            self.presentViewController(activityController, animated: true, completion: nil)
            let presCon = activityController.popoverPresentationController
            presCon?.barButtonItem = barButton
        }
        else {
            print("not a bar button!")
        }
        
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        let open = OpenIn(barButton: shareButton)
        if let fileURL = NSBundle.mainBundle().URLForResource("MyImage", withExtension: "jpg") {
            activityController = UIActivityViewController(activityItems: [fileURL], applicationActivities: [open])
            
        }
            
        else {
            print("file missing!")
        }
        
    }
    
}