Use of Unresolved Identifier firebase function - swift

Question

I've defined the function sendDataToDatabase but for some reason it's not resolving photoUrl?
I've been trying to figure out what might be causing this for 6 hours now and can't seem to find a solution, if anyone could provide some help it would be appreciated.
#IBAction func shareButton_TouchUpInside(_ sender: Any) {
ProgressHUD.show("Waiting...", interaction: false)
if let profileImg = self.selectedImage, let imageData = profileImg.jpegData(compressionQuality: 0.1) {
let photoId = NSUUID().uuidString
let storageRef = Storage.storage().reference(forURL: "manifest-bit-233115.appspot.com").child("posts").child(photoId)
storageRef.putData(imageData, metadata: nil, completion: { (metadata, Error) in
if Error != nil {
return
}
storageRef.downloadURL(completion: { (URL, Error) -> Void in
if (Error != nil) {
//handle any errors
} else {
//get download url
let photoUrl = URL?.absoluteString
}
self.sendDataToDatabase(photoUrl: photoUrl!)
})
}
)}
func sendDataToDatabase(photoUrl: photoUrl!) {
let ref = Database.database().reference()
//let uid = Auth.auth().currentUser!.uid
let postsRef = ref.child("posts")
let newPostId = postsRef.childByAutoId().key
let newPostRef = postsRef.child(newPostId!)
newPostRef.setValue(["photoUrl": photoUrl])
}

Answer 1

There are many issues.
You have to call sendDataToDatabase only in the else branch and declare the parameters with starting lowercase letters.
The parameters are not types.
storageRef.downloadURL(completion: { (url, error) -> Void in
if let error = error {
//handle any errors
} else {
//get download url
let photoUrl = url!.absoluteString
self.sendDataToDatabase(photoUrl: photoUrl)
}
})
and you have to declare the type in the function
func sendDataToDatabase(photoUrl: String) { ...

Answer 2

This won't work:
storageRef.downloadURL(completion: { (URL, Error) -> Void in
if (Error != nil) {
//handle any errors
} else {
//get download url
let photoUrl = URL?.absoluteString
}
self.sendDataToDatabase(photoUrl: photoUrl!)
})
photoUrl will only be available within the else clause, since that's where it's defined, and you can not use it outside of that scope.
Also, this:
func sendDataToDatabase(photoUrl: photoUrl!)
should probably be:
func sendDataToDatabase(photoUrl: String)
It's also a good idea to not name variables URL and Error, since they are identical to the URL and Error classes. Name them url and error instead.