Why Dispatch Group Notify get's called twice?

Question

I'm trying to get my app to use dispatch groups to make sure all invites have been sent before continuing. I thought the notify callback only got called once all enters have a matching leave but mine appears to be getting called multiple times, here's my code:

    for invite in invites {
        dispatchGroup.enter()
        let ref = FIRDatabase.database().reference().child("users").child(invite.id).child("invites")
        print(invite)
        ref.updateChildValues([name: nameTextField.text!]) { (error, ref) -> Void in
            dispatchGroup.leave()

            dispatchGroup.notify(queue: DispatchQueue.main, execute: {
                print("YOYOYO")
            })
        }
    }

In my console I'm seeing 2 "YOYOYO"s which confused me. Can anybody let me know if I'm doing this incorrectly or are my assumptions wrong?

Answer 1

You probably have two invites. Move dispatchGroup.notify out of the for loop if you want to get notified after all invites are processed:

for invite in invites {
    dispatchGroup.enter()
    let ref = FIRDatabase.database().reference().child("users").child(invite.id).child("invites")
    print(invite)
    ref.updateChildValues([name: nameTextField.text!]) { (error, ref) -> Void in
        dispatchGroup.leave()            
    }
}

dispatchGroup.notify(queue: DispatchQueue.main) {
    print("YOYOYO")
}