macOS screenshots Photos access via MLMediaLibrary

MediaLibraryAccess.swift

import Cocoa
import MediaLibrary

/// requires NSPhotoLibraryUsageDescription in info.plist
/// requires Pictures access in sandbox settings
final class PhotoSource: NSObject {
    let photosLibrary = MLMediaLibrary(options: [
        MLMediaLoadSourceTypesKey: MLMediaSourceType.image.rawValue,
        MLMediaLoadIncludeSourcesKey: [MLMediaSourcePhotosIdentifier],
        MLMediaLoadExcludeSourcesKey: [MLMediaSourcePhotoBoothIdentifier],
        ])
    private var mediaSources: [String: MLMediaSource] = [:] {
        didSet {
            photoSource = mediaSources[MLMediaSourcePhotosIdentifier]
        }
    }
    var photoSource: MLMediaSource? {
        didSet {
            NSLog("photoSource = %@", photoSource.debugDescription)
            guard let s = photoSource else { return }

            kvos.append(s.observe(\.rootMediaGroup, options: .new) { [unowned self] _, _ in
                self.rootMediaGroup = self.photoSource?.rootMediaGroup
            })
            _ = s.rootMediaGroup // async load
        }
    }
    var rootMediaGroup: MLMediaGroup? {
        didSet {
            NSLog("rootMediaGroup = %@", rootMediaGroup.debugDescription)
            guard let g = rootMediaGroup else { return }

            screenshotGroup = g.childGroups?
                .first {$0.typeIdentifier == MLPhotosAlbumsGroupTypeIdentifier}?
                .childGroups?
                .first {$0.typeIdentifier == MLPhotosScreenshotGroupTypeIdentifier}
        }
    }
    var screenshotGroup: MLMediaGroup? {
        didSet {
            NSLog("screenshotGroup = %@", screenshotGroup.debugDescription)
            guard let g = screenshotGroup else { return }

            kvos.append(g.observe(\.mediaObjects, options: .new) { [unowned self] _, _ in
                self.screenshots = self.screenshotGroup?.mediaObjects ?? []
            })
            _ = g.mediaObjects // async load
        }
    }
    @objc dynamic var screenshots: [MLMediaObject] = [] {
        didSet {
//            NSLog("screenshots = %@", screenshots.debugDescription)
            NSLog("%d screenshots", screenshots.count)
        }
    }

    private var kvos: [NSKeyValueObservation] = []

    override init() {
        super.init()
        kvos.append(photosLibrary.observe(\.mediaSources) { [unowned self] _, _ in
            self.mediaSources = self.photosLibrary.mediaSources ?? [:]
        })
        _ = photosLibrary.mediaSources // async load
    }
}

class ViewController: NSViewController {
    let photoSource = PhotoSource()
    private var kvos: [NSKeyValueObservation] = []

    private var screenshots: [MLMediaObject] = [] {
        didSet {
            guard let sample = screenshots.last else { return }
            // requires thumbnailURL access (sandbox related)
            guard let thumbnail = (sample.thumbnailURL.flatMap {try? Data(contentsOf: $0)}) else { return }
            self.view.layer?.contents = NSImage(data: thumbnail)
            self.view.layer?.contentsGravity = .resizeAspect
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        kvos.append(photoSource.observe(\.screenshots, options: .new) { [unowned self] _, _ in
            self.screenshots = self.photoSource.screenshots
        })
    }
}