added savePhotoOnLongPress function

[alexookah]

Created this function so that users can easily use a simple default UIAlertController with two options:
Save Photo and Cancel

using it in just one single line:
agrume.onLongPress = agrume.photoSavedToLibrary

I didnt add it as a default longPress function because some user's might not want this and also they might have not have NSPhotoLibraryUsageDescription and NSPhotoLibraryAddUsageDescription in their info.plist.

@JanGorman
Tell me what you think about this. If it needs some change or any suggestion how to improve.

I was thinking to add some documentation in the readme after this gets merged to master 👍

[alexookah]

@JanGorman
maybe if this is okay to merge then i think it would be nice to add a right Button on navigationbar "..." to show users visually that they can also download an image or some other function callback users pass in agrume :)

[JanGorman]

I'll need some quiet time to go over this. I'll take a look on the weekend :)

[alexookah]

@JanGorman did you have a chance to take a look?

[JanGorman]

Overall it's nice to provide an easy way to add save functionality but what I don't quite like is that this is then so "hardcoded" in a more general purpose library. It's a leaky abstraction to have the save and cancel title properties as well as the completion handler. What I'd propose to do instead is the following:

1. Change the onLongPress to the following: public var onLongPress: ((UIImage?, UIViewController) -> Void)? – this makes it more useful anyway because you can easily access the image and controller

2. Put the save functionality into a completely separate class. I quickly tried this and what it could look like is this:

import UIKit

public final class AgrumePhotoLibraryHelper: NSObject {

  private let saveButtonTitle: String
  private let cancelButtonTitle: String
  private let saveToLibraryHandler: (_ error: Error?) -> Void

  public init(saveButtonTitle: String, cancelButtonTitle: String, saveToLibraryHandler: @escaping (_ error: Error?) -> Void) {
    self.saveButtonTitle = saveButtonTitle
    self.cancelButtonTitle = cancelButtonTitle
    self.saveToLibraryHandler = saveToLibraryHandler
  }

  public func makeLongPressGesture(for image: UIImage?, viewController: UIViewController) {
    guard let image = image else {
      return
    }
    let view = viewController.view!
    let alert = UIAlertController(title: nil, message: nil, preferredStyle: .actionSheet)
    alert.popoverPresentationController?.sourceView = view
    alert.popoverPresentationController?.permittedArrowDirections = .up
    let alertPosition = CGRect(x: view.bounds.midX, y: view.bounds.maxY - view.bounds.midY / 2, width: 0, height: 0)
    alert.popoverPresentationController?.sourceRect = alertPosition

    alert.addAction(UIAlertAction(title: saveButtonTitle, style: .default) { _ in
      UIImageWriteToSavedPhotosAlbum(image, self, #selector(self.image), nil)
    })
    alert.addAction(UIAlertAction(title: cancelButtonTitle, style: .cancel, handler: nil))

    viewController.present(alert, animated: true)
  }

  @objc
  private func image(_ image: UIImage, didFinishSavingWithError error: NSError?, contextInfo: UnsafeRawPointer) {
    saveToLibraryHandler(error)
  }

}

So we put the button titles into properties here, as well as the completion handler. Then, to invoke it:

private func makeHelper() -> AgrumePhotoLibraryHelper {
    let saveButtonTitle = NSLocalizedString("Save Photo", comment: "Save Photo")
    let cancelButtonTitle = NSLocalizedString("Cancel", comment: "Cancel")
    let helper = AgrumePhotoLibraryHelper(saveButtonTitle: saveButtonTitle, cancelButtonTitle: cancelButtonTitle) { error in
      guard error == nil else {
        print("Could not save your photo")
        return
      }
      print("Photo has been saved to your library")
    }
    return helper
  }

and when you want to add the gesture, you do

let helper = makeHelper()
agrume.onLongPress = helper.makeLongPressGesture

This is marginally more code on client side but a cleaner abstraction

[alexookah]

@JanGorman You were absolutely right. Thanks for your proposed changes.
I think i made all of them.

[alexookah]

@JanGorman
Oh yes, missed that. Sorry.
How do you run the Example? it needs SwiftyGif and there is no PodFile to run podInstall.

[JanGorman]

ah… good to know that it's not so evident. Need to document that. I don't like the CocoaPods default directory layout so for the example I opted to add this as git submodule. To run the example from the project root dir run git submodule update --init and then you can compile

[JanGorman]

SingleURLViewController still has a small bug

[alexookah]

@JanGorman Finally i can run the example thank you. Yes this should be in the Documentation.

Are you sure? i did one more commit after my previous comment

[JanGorman]

Didn't have the latest state. Cool, thanks a lot for the addition

[alexookah]

@JanGorman sorry for all these commits.
So Is this okay now for merge?

[JanGorman]

Got pulled into a meeting 😝. Yes, good to go