ios - How to delete a child from Firebase (Swift)

Question

I've been following a tutorial on making an instragram-esque app, and I'm having a lot of trouble figuring out how to delete a post, both from Firebase and from the feed. The image that the user selects or takes is uploaded to Firebase database with this function:

func uploadToFirebase() {
    AppDelegate.instance().showActivityIndicator()

    let uid = FIRAuth.auth()!.currentUser!.uid
    let ref = FIRDatabase.database().reference()
    let storage = FIRStorage.storage().reference(forURL: "gs://cloudcamerattt.appspot.com")

    let key = ref.child("posts").childByAutoId().key
    let imageRef = storage.child("posts").child(uid).child("(key).jpg")

    let data = UIImageJPEGRepresentation(self.previewImage.image!, 0.6)

    let uploadTask = imageRef.put(data!, metadata: nil) { (metadata, error) in

        if error != nil {
            print(error!.localizedDescription)
            AppDelegate.instance().dismissActivityIndicator()
            return
        }

        imageRef.downloadURL(completion: { (url, error) in

            if let url = url {
                // how do I add date: NSDate in here?
                let feed = ["userID" : uid,
                            "pathToImage" : url.absoluteString,
                            "likes" : 0,
                            "author" : FIRAuth.auth()!.currentUser!.displayName!,
                            "postID" : key] as [String : Any]

                let postFeed = ["(key)" : feed]

                ref.child("posts").updateChildValues(postFeed)
                AppDelegate.instance().dismissActivityIndicator()

                self.dismiss(animated: true, completion: nil)
            }
        })
    }
    uploadTask.resume()
}

Which ends up in Firebase looking like this:

Following a stack overflow answer I found, I tried to set up a delete function to be called when the delete button is pressed. This delete button is on a "photo detail" view, which the user gets to by tapping an image in the image feed - this photo detail view displays the image in a bigger size, along with some other info such as likes:

func deletePost(firstTree: String, childIWantToRemove: String) {

    let uid = FIRAuth.auth()!.currentUser!.uid
    let ref = FIRDatabase.database().reference()
    let storage = FIRStorage.storage().reference(forURL: "gs://cloudcamerattt.appspot.com")

    let key = ref.child("posts").childByAutoId().key
    let imageRef = storage.child("posts").child(uid).child("(key).jpg")

    ref.child("posts").child(key).child("postID").removeValue { (error, ref) in
        if error != nil {
            print("error (error)")
        }
    }
}

And call the function here:

@IBAction func moreButtonPressed(_ sender: AnyObject) {

    let alertController = UIAlertController(title: nil, message: nil, preferredStyle: .actionSheet)
    let cancelAction = UIAlertAction(title: "Cancel", style: .cancel)
    let destroyAction = UIAlertAction(title: "Delete", style: .destructive) { action in
        print(action)

        let ref = FIRDatabase.database().reference()
        let key = ref.child("posts").childByAutoId().key

        let firstTree = key
        let valueToRemove = "postID"
        self.deletePost(firstTree: firstTree, childIWantToRemove: valueToRemove)
    }

    alertController.addAction(destroyAction)
    alertController.addAction(cancelAction)
    self.present(alertController, animated: true)
}

I'm not really understanding what I'm doing though, and needless to say tapping the delete button does essentially nothing. Can anyone show me how to fix the delete function so I can remove an image/post from firebase properly?

EDIT: I have var selectedPost: Post! in my PhotoDetailController, which is passed from the FeedViewController (image feed) in didSelectItem like so:

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    let photoDetailController = self.storyboard?.instantiateViewController(withIdentifier: "photoDetail") as! PhotoDetailController

    photoDetailController.selectedPost = posts[indexPath.row]

    present(photoDetailController, animated: true, completion: nil)
}

So it has the index path. Another note about the above function is that var posts = [Post]() is instantiated in the FeedViewController, so that's where posts[indexPath.row] comes from.

Answer 1

Waitting for answers