Be Careful with "UI API called on a background thread"

File

self.view.makeToastActivity(.center)
DispatchQueue.global(qos: .background).async {
    if let url = URL(string: self.photo.url),
        let urlData = NSData(contentsOf: url)
    {
        let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0];
        let filePath="\(documentsPath)/tempFile.mp4"
        urlData.write(toFile: filePath, atomically: true)
        PHPhotoLibrary.shared().performChanges({
            let assetChangeRequest = PHAssetChangeRequest.creationRequestForAssetFromVideo(atFileURL: URL(fileURLWithPath: filePath))
            let albumChangeRequest = PHAssetCollectionChangeRequest(for: CustomPhotoAlbum.sharedInstance.assetCollection)
            albumChangeRequest!.addAssets([assetChangeRequest!.placeholderForCreatedAsset!] as NSArray)
        }) { completed, error in
            if completed {
                print("Video is saved!")
            }
            DispatchQueue.main.async {
                self.view.hideToastActivity()
                self.view.makeToast(self.messages.social_downloaded, duration: 2.0, position: .center)
            }
        }
    }
}