从 firebase 调用数据时 void 函数中出现意外的非 void return 值

Question

我正在尝试从 firebase 调用数据，将图像视图更改为数据库中存储的图像视图。当我调用我的代码时，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
}()

注释掉的 return 函数所在的位置，我收到错误 Use of unresolved identifier 'profileImageView';你是说 'provideImageData' 吗？为什么？我假设由于 return 在闭包内，它会知道 profileImageView 是什么。

Answer 1

分离图像视图和实时数据库侦听器：

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")
    })

从 firebase 调用数据时 void 函数中出现意外的非 void return 值

Unexpected non-void return value in void function while calling data from firebase

imageview

firebase

swift

firebase-realtime-database