我想将图像的下载URL放入Firebase数据库中。我可以将图像上传到存储中，但无法弄清楚如何将URL与其余的“帖子”一起放入数据库。

@IBOutlet weak var titleText: UITextField!
@IBOutlet weak var authorText: UITextField!
@IBOutlet weak var mainText: UITextView!
@IBOutlet weak var dateText: UITextField!
@IBOutlet weak var myImageView: UIImageView!

var ref:FIRDatabaseReference?

override func viewDidLoad() {
    super.viewDidLoad()

    ref = FIRDatabase.database().reference()

}


override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}


@IBAction func uploadImage(_ sender: Any) {


       let image = UIImagePickerController()
    image.delegate = self
    image.sourceType = UIImagePickerControllerSourceType.photoLibrary

    image.allowsEditing = false

    self.present(image, animated: true)
    {
        //after its completed
    }
}


@objc(imagePickerController:didFinishPickingMediaWithInfo:) func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any])
{
    if let image = info[UIImagePickerControllerOriginalImage] as? UIImage
    {
        myImageView.image = image

    }
    else
    {
        //error
    }

    self.dismiss(animated: true, completion: nil)

    let storageRef = FIRStorage.storage().reference().child("myImage.png")
    if let uploadData = UIImagePNGRepresentation(self.myImageView.image!){
        storageRef.put(uploadData, metadata: nil, completion:
            {
                (metadata, error) in
                if error != nil {
                    print("error")
                    return
                }

   print(metadata)

   //how do I put the download URL in the metadata into my database

        }  
        )
    }

}

@IBAction func addPost(_ sender: Any) {

    if self.titleText.text != "" && self.authorText.text != "" && self.mainText.text != "" && self.dateText.text != ""
    {

        ref?.child("Posts").childByAutoId().setValue(["Title": titleText.text,"Article": mainText.text, "Author": authorText.text, "Date": dateText.text, "myImageURL": myImageURL])

        //the myImageURL part is where I get an error

        self.performSegue(withIdentifier: "post", sender: self)

    }
    else{

        let alertController = UIAlertController(title: "Oops!", message: "Field left blank", preferredStyle: .alert)

        let defaultAction = UIAlertAction(title: "Ok", style: .cancel, handler: nil)
        alertController.addAction(defaultAction)

        self.present(alertController, animated: true, completion: nil)

        }
    }
}