UNNotificationAttachment with UIImage or Remote URL

Question

In my Notification Service Extension I am downloading an image from a URL to show as UNNotificationAttachment in a notification.

So I have

Answer 1

1. create directory in tmp folder
2. write the NSData representation of the UIImage into the newly created directory
3. create the UNNotificationAttachment with url to the file in tmp folder
4. clean up tmp folder

I wrote an extension on UINotificationAttachment

extension UNNotificationAttachment {

    static func create(identifier: String, image: UIImage, options: [NSObject : AnyObject]?) -> UNNotificationAttachment? {
        let fileManager = FileManager.default
        let tmpSubFolderName = ProcessInfo.processInfo.globallyUniqueString
        let tmpSubFolderURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(tmpSubFolderName, isDirectory: true)
        do {
            try fileManager.createDirectory(at: tmpSubFolderURL, withIntermediateDirectories: true, attributes: nil)
            let imageFileIdentifier = identifier+".png"
            let fileURL = tmpSubFolderURL.appendingPathComponent(imageFileIdentifier)
            let imageData = UIImage.pngData(image)
            try imageData()?.write(to: fileURL)
            let imageAttachment = try UNNotificationAttachment.init(identifier: imageFileIdentifier, url: fileURL, options: options)
            return imageAttachment
        } catch {
            print("error " + error.localizedDescription)
        }
        return nil
    }
}

So to create UNUserNotificationRequest with UNUserNotificationAttachment from a UIImage you can simply do sth like this

let identifier = ProcessInfo.processInfo.globallyUniqueString
let content = UNMutableNotificationContent()
content.title = "Hello"
content.body = "World"
if let attachment = UNNotificationAttachment.create(identifier: identifier, image: myImage, options: nil) {
    // where myImage is any UIImage
    content.attachments = [attachment] 
}
let trigger = UNTimeIntervalNotificationTrigger(timeInterval: 120.0, repeats: false)
let request = UNNotificationRequest.init(identifier: identifier, content: content, trigger: trigger)
UNUserNotificationCenter.current().add(request) { (error) in
    // handle error
}

This should work since UNNotificationAttachment will copy the image file to an own location.