“ StorageMetadata”没有成员“ downloadURL”

Question

因此，我在我的学校项目中尝试解决了一段时间的代码中出现了2个错误，但是由于我不习惯于快速编程，所以我一直无法解决它（我从YouTube教程中获取了代码）。第一个是“'StorageMetaData'的值没有成员'downloadURL'（在func uploadImg里面）。然后另一个错误是”使用未解析的标识符'imagePicker'（在@IBAction func selectedImgPicker的末尾）。 这是我的代码：

class SignUpVC: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {
    @IBOutlet weak var userImagePicker: UIImageView!
    @IBOutlet weak var usernameField: UITextField!
    @IBOutlet weak var signUpBtn: UIButton!

    var userUid: String!
    var emailField: String!
    var passwordField: String!
    var imagePicker: UIImagePickerController!
    var imageSelected = false
    var username: String!

    override func viewDidLoad() {
        super.viewDidLoad()

        imagePicker.delegate = self as? UIImagePickerControllerDelegate & UINavigationControllerDelegate
        imagePicker = UIImagePickerController()
        imagePicker.allowsEditing = true
    }

    override func viewDidDisappear(_ animated: Bool) {
        if let _ = KeychainWrapper.standard.string(forKey: "uid"){
            performSegue(withIdentifier: "Message", sender: nil)
        }
    }

    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]){
        if let image = info[UIImagePickerControllerEditedImage] as? UIImage{
            userImagePicker.image = image
            imageSelected = true
        } else {
            print("image wasnt selected")
        }
        imagePicker.dismiss(animated: true, completion: nil)
    }

    func setUser(img: String){
        let userData = ["username": username!, "userImg": img]

        KeychainWrapper.standard.set(userUid, forKey: "uid")

        let location = Database.database().reference().child("users").child(userUid)
        location.setValue(userData)
        dismiss(animated: true, completion: nil)
    }

    func uploadImg(){
        if usernameField.text == nil {
            signUpBtn.isEnabled = false
        } else {
            username = usernameField.text
            signUpBtn.isEnabled = true
        }
        guard let img = userImagePicker.image, imageSelected == true else{
            print("image needs to be selected")
            return
        }
        if let imgData = UIImageJPEGRepresentation(img, 0.2){
            let imgUid = NSUUID().uuidString
            let metadata = StorageMetadata()
            metadata.contentType = "image/jpeg"
            Storage.storage().reference().putData(imgData, metadata: metadata){
                (metadata, error) in

                if error != nil{
                    print("did not upload image")
                }else{
                    print("uploaded")

                    let downloadURL = metadata?.downloadURL()?.absoluteString

                    if let url = downloadURL{
                        self.setUser(img: url)
                    }
                }
                }
            }
        }

    @IBAction func createAccount(_ sender: AnyObject){
        Auth.auth().createUser(withEmail: emailField, password: passwordField, completion: {
            (user, error) in
            if error != nil {
                print("Cant create user")
            } else {
                if let user = user {
                    self.userUid = user.user.uid
                }
            }
            self.uploadImg()
        })
    }

    @IBAction func selectedImgPicker (_ sender: AnyObject){
        present(imagePicker, animated: true, completion: nil)
    }

    @IBAction func cancel (_ sender: AnyObject){
        dismiss(animated: true, completion: nil)
    }
}