AssetsHelper.swift

import Photos

class AssetsHelper {
    class func addAsset(image: UIImage, completion: @escaping (_ identifier: String?) -> Void) {
        var identifier: String?
        PHPhotoLibrary.shared().performChanges({
            let request = PHAssetChangeRequest.creationRequestForAsset(from: image)
            identifier = request.placeholderForCreatedAsset?.localIdentifier
        }) { success, error in
            guard success == true,
                let identifier = identifier else {
                    completion(nil)
                    return
            }
            completion(identifier)
        }
    }
}