Getting error "Variable used within its own initial value" - swift

Question

I am writing a new bit of code that allows a user to upload an image to a post that will be saved in Firebase database and storage. Then it will be shown in a UITableView on a separate Viewcontroller. On the part of code where I want to save the photo url to my database I am getting an error "Variable used within its own initial value". I have looked at other threads covering this issue and when I follow their advice I get a new set of errors. Here is what my code looks like and where I am getting the error. If there are any suggestions that would be great, thank you!
Here is code:
func postWithImageAndText() {
var imagesArray = [AnyObject]()
let postLength = textView.text.count
let numImages = imagesArray.count
let postRef = Database.database().reference().child("posts").childByAutoId()
let storageRef = Storage.storage().reference()
let uid = Auth.auth().currentUser
let pictureStorageRef = storageRef.child("users/profile/\(uid)/media")
let lowResImageData = (imagesArray[0] as! UIImage).jpegData(compressionQuality: 0.50)
if(postLength>0 && numImages>0)
{
let uploadTask = pictureStorageRef.putData(lowResImageData!,metadata: nil)
{metadata,error in
if (error == nil) {
let downloadUrl = storageRef.downloadURL { (url, error) in
guard let userProfile = UserService.currentUserProfile else { return }
let childUpdates = [
"author": [
"uid": userProfile.uid,
"username": userProfile.fullname,
"photoURL": userProfile.photoURL.absoluteString
],
"text": self.textView.text!,
"picture": downloadUrl!.absoluteString,
"timestamp": ["sv.":"timestamp"]
] as [String:Any]
}
}
}
}
}
`
Error is happening on this part: "picture": downloadUrl!.absoluteString,

Answer 1

As i can see yo got an "Variable used within its own initial value" error, that means you try to access initial value of variable within this variable, its not a good behavior.
I also see you dont use any data from your completion block, so try to use nil instead of your completion block and then try to access your downloadURL variable

Answer 2

Your updated code:
func postWithImageAndText() {
var imagesArray = [AnyObject]()
let postLength = textView.text.count
let numImages = imagesArray.count
let postRef = Database.database().reference().child("posts").childByAutoId()
let storageRef = Storage.storage().reference()
let uid = Auth.auth().currentUser
let pictureStorageRef = storageRef.child("users/profile/\(uid)/media")
if let lowResImageData = (imagesArray[0] as! UIImage).jpegData(compressionQuality: 0.50) {
if(postLength>0 && numImages>0)
{
pictureStorageRef.putData(lowResImageData, metadata: metaData) { (metadata, error) in
if error != nil {
print("Failed to upload image:", error as Any)
}
pictureStorageRef.downloadURL(completion: { (url, error) in
if error != nil {
print(error!)
}
if let imageUrl = url?.absoluteString {
guard let userProfile = UserService.currentUserProfile else { return }
let childUpdates = [
"author": [
"uid": userProfile.uid,
"username": userProfile.fullname,
"photoURL": userProfile.photoURL.absoluteString
],
"text": self.textView.text!,
"picture": imageUrl,
"timestamp": ["sv.":"timestamp"]
] as [String:Any]
}
})
}
}
}
}