Swift Firebase图像0个字节

Question

我有一个应该处理下载图像的方法.除了从Firebase存储返回的数据是0字节之外,它似乎完全正常工作.为什么是这样？

 func useDatabaseToDownloadPicture () {
     if let userId = FIRAuth.auth()?.currentUser?.uid {

    // Get a reference to the storage service using the default Firebase App
    let storage = FIRStorage.storage()

        let firebaseImages = FIRStorage.storage().reference().child("Images")
        let userPhotoLocation = firebaseImages.child("Users").child(userId).child("profilePicture.jpg")
        let myRef = FIRStorage.storage().reference()
        let firebaseProfilePicLocation = firebase.child("Users").child(userId).child("Images").child("profilePicture").child("downloadURL")

    firebaseProfilePicLocation.observe(.value, with: { (snapshot) in
        print(" Profile Picture Databse Snapshot -> \n \(snapshot) ")
        // Get download URL from snapshot
        if let downloadURL = snapshot.value as? String {
             print(" downloadURL converted to String ")

        // Create a storage reference from the URL
        let storageRef = storage.reference(forURL: downloadURL)

        // Download the data, assuming a max size of 1MB (you can change this as necessary)
        storageRef.data(withMaxSize: 1 * 1024 * 1024) { (data, error) -> Void in
            print("Downloading Data . . . Data String -> \(String(describing: data))")
            print("Downloading Data . . . Data Literal -> \(data)")
            // Create a UIImage, add it to profile picture
            if data != nil {
            print("Data is not nil!")
                if let image = UIImage(data: data!) {
                    print("Image Created")
                } else {
                    print("Image Could Not create!! check data...")
                    let url = URL(string: downloadURL)
                    let urlData = try? Data(contentsOf: url!)
                    if let img = UIImage(data: urlData!) {
                        print("Image  2 Created")
                    } else {
                        print("Image 2 Failed")
                    }
                }
            let pic = UIImage(data: data!)
            self.profilePicture.image = pic
            } else {
                print(" ? Data is nil ")
            }
        }



        } else if let downloadURL = snapshot.value as? URL {
              print(" downloadURL converted to URL! ")

                // Create a storage reference from the URL
                let storageRef = storage.reference(forURL: downloadURL.absoluteString)

                // Download the data, assuming a max size of 1MB (you can change this as necessary)
                storageRef.data(withMaxSize: 1 * 1024 * 1024) { (data, error) -> Void in
                    // Create a UIImage, add it to profile picture
                    if data != nil {
                        let pic = UIImage(data: data!)
                        self.profilePicture.image = pic
                    } else {
                        print(" ? Data is nil")
                    }
                }
        } else {

             // . . . Do nothing, all ways failed
        }

    })
    }
}

打印结果是:

downloadURL converted to String
Downloading Data . . . Data String -> Optional(0 bytes)
Downloading Data . . . Data Literal -> Optional(0 bytes)
Image Could Not create!! check data...
Image 2 Failed

对我来说,似乎问题是正确的数据进入,但似乎问题是数据是0字节.为什么会这样？

谢谢!!