從 firebase 調用數據時，void 函數中出現意外的非空返回值

Question

我正在嘗試從 firebase 調用數據，該數據將圖像視圖更改為存儲在數據庫中的視圖。 當我調用我的代碼時，我看到

let image: UIImageView = {
    let uid = Auth.auth().currentUser?.uid
    Database.database().reference().child("users").child(uid!).observeSingleEvent(of: .value, with: { (snapshot) in
        guard let dictionary = snapshot.value as? [String : Any] else {
            return }
        let user = MyUser(dictionary: dictionary as [String : AnyObject])
        let profileImageView = UIImageView()
        profileImageView.translatesAutoresizingMaskIntoConstraints = false
        profileImageView.contentMode = .scaleAspectFill
        profileImageView.layer.cornerRadius = 30
        profileImageView.clipsToBounds = true
        profileImageView.image = UIImage(named: "app")
        profileImageView.image=#imageLiteral(resourceName: "user")
        profileImageView.loadImageUsingCacheWithUrlString(user.profileImageUrl!)
        return profileImageView
    }, withCancel: { (err) in
        print("attempting to load information")
    })
    //  return profileImageView
}()

注釋掉的返回函數在哪里，我收到錯誤 Use of unresolved identifier 'profileImageView'; 你的意思是'provideImageData'？ 為什么？ 我會假設由於返回在閉包內，它會知道 profileImageView 是什么。

Answer 1

分離圖像視圖和實時數據庫監聽器：

let imageView: UIImageView {
        let imageView = UIImageView()
        imageView.translatesAutoresizingMaskIntoConstraints = false
        imageView.contentMode = .scaleAspectFill
        imageView.layer.cornerRadius = 30
        imageView.clipsToBounds = true
        return imageView
}

let uid = Auth.auth().currentUser?.uid
Database.database().reference().child("users").child(uid!).observeSingleEvent(of: .value, with: { (snapshot) in
        guard let dictionary = snapshot.value as? [String : Any] else {
            return }
        let user = MyUser(dictionary: dictionary as [String : AnyObject])
        // Set the image view's image
        imageView.image = // ...
    }, withCancel: { (err) in
        print("attempting to load information")
    })