从 firebase 调用数据时，void 函数中出现意外的非空返回值

Question

I am trying to call data from firebase that changes the image view to be that of what is stored in the database. when I call my code, I see

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
}()

where the commented out return function is, I am getting the error Use of unresolved identifier 'profileImageView'; did you mean 'provideImageData'? why? I would assume that since the return is within the closures, it would know what profileImageView is.

Answer 1

Separate the image view and the real time database listener:

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")
    })