[Swift] Get the size (ContentLength) of an http remote file

fetchContentLength.swift

func fetchContentLength(for url: URL, completionHandler: @escaping (_ contentLength: UInt64?) -> ()) {
    
  var request = URLRequest(url: url)
  request.httpMethod = "HEAD"
    
  let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
    guard error == nil,
      let response = response as? HTTPURLResponse,
      let contentLength = response.allHeaderFields["Content-Length"] as? String else {
        completionHandler(nil)
        return
    }
    completionHandler(UInt64(contentLength))
  }
    
  task.resume()
}

let url = URL(string: "https://s3.amazonaws.com/x265.org/video/Tears_400_x265.mp4")!

fetchContentLength(for: url, completionHandler: { (contentLength) in
  print(contentLength ?? 0)
})