Tarvo Mäesepp Tarvo Mäesepp - 3 years ago 135
Swift Question

Unrecognized selector while removing all user posts from Firebase

I tried to delete all posts that belongs to specific user, however it crashes telling me error:

'-[FIRDataSnapshot removeValue]: unrecognized selector sent to
instance 0x174238c20'

but if I try to
the child, it prints out the child.

That is how I am doing it in Swift3:

FIRDatabase.database().reference().child("posts").queryEqual(toValue: self.currentUser.generalDetails.userName).ref.observe(.value, with: { (snapshot: FIRDataSnapshot!) in
for child in snapshot.children {
(child as AnyObject).removeValue() //This line gives the error.

That is the child that shold be removed if

-KUaMd3YgJlQvv_P-kdK//This has to be deletod with all its children
postImageStringUrl: close

Wha should cause the crash?

Edit: I updated code like this which says that I have to :

Consider adding ".indexOn": "posts/username" at / to your security
rules for better performance

however I have pretty ok security rules:

"rules": {
".read": "auth != null",
".write": "auth != null",
"Snuses": {
".indexOn": ["Brand", "posts/username"]
FIRDatabase.database().reference().queryOrdered(byChild: "posts/username").queryEqual(toValue: currentUser.generalDetails.userName)
.observeSingleEvent(of: .value, with: { snapshot in

if ( snapshot.value is NSNull ) {
print("not found")
} else {
for child in (snapshot.children) {
let element = child as! FIRDataSnapshot //the node data
let key = element.key //the key for the node
let nodeToRemove = FIRDatabase.database().reference().child(key)

Jay Jay
Answer Source

I believe you are going to want to remove child by it's parent key, not the child.

Frank provided a short comment (which is actually THE answer) but here's a verbose example (Firebase 2.x but you'll get the idea):

ref.queryOrdered(byChild: "posts/username").queryEqual(toValue: "someUsername")
     .observeSingleEvent(of: .value, with: { snapshot in

     if ( snapshot?.value is NSNull ) {
           print("not found")
     } else {
           for child in (snapshot?.children)! {
                let element = child as! FDataSnapshot //the node data
                let key = element.key! //the key for the node
                let nodeToRemove = ref.child(byAppendingPath: key)

something to look for is to make sure your paths are correct.

In the above code, 'key' is the parent node name like


If you were to use

let ref = element.ref

it would be the specific path to that node, including the node name but no other data, like this


so the idea is once you have that reference, use use the reference to remove the node.

So if ref = root_node/posts/-KUaMd3YgJlQvv_P-kdK

then ref.remove(), it will remove that reference and the child data.

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