download File From Web with Alamofire

downloadFile.swift

func downloadFile(from remoteURL: URL, completion: @escaping (_ localURL: URL) -> Void) {
    let documentsDirectoryURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
    let destinationUrl = documentsDirectoryURL.appendingPathComponent(randomString)

    if FileManager.default.fileExists(atPath: destinationUrl.path) {
        DispatchQueue.main.async { completion(destinationUrl) }; return
    }
    URLSession.shared.downloadTask(with: remoteURL, completionHandler: { (location, response, error) -> Void in
        guard let location = location, error == nil else { return }
        do {
            try FileManager.default.moveItem(at: location, to: destinationUrl)
            DispatchQueue.main.async { completion(destinationUrl) }
        } catch let error as NSError { print(error) }
    }).resume()
}