swift wait until array is set before calling function - swift

Question

I would like to call fetchArrayOfUsersBlockingTheCurrentUser() and wait until the array of blocked users is complete before calling fireStoreFetchUsers(), as I would like to dismiss blocked users from the usersarray before loading the users on the screen.
so far the screen loads all users before the array is set and only work when leaving the screen and coming back to the screen
I have tried did set but it calls fetchusers to many times putting the same user multiple times on the screen.
code below:
func fetchArrayOfUsersBlockingTheCurrentUser() {
guard let uid = Auth.auth().currentUser?.uid else { return }
let db = Firestore.firestore()
let docRef = db.collection("Users").document(uid).collection("Users Blocking Me")
docRef.getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
let d = document.documentID
self.UsersBlockingCurrentUserArray.append(d)
}
}
}
fireStoreFetchUsers()
}
var UsersBlockingCurrentUserArray = [String]()
var users = [User2]()
and the function fireStoreFetchUsers() basically goes;
///fetche users from database
///users.append(user)
//reload data

Answer 1

Don't wait. Move fireStoreFetchUsers() into the completion block.
func fetchArrayOfUsersBlockingTheCurrentUser() {
guard let uid = Auth.auth().currentUser?.uid else { return }
let db = Firestore.firestore()
let docRef = db.collection("Users").document(uid).collection("Users Blocking Me")
docRef.getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
let d = document.documentID
self.UsersBlockingCurrentUserArray.append(d)
}
self.fireStoreFetchUsers()
}
}
}
And please conform to the naming convention that variable names start with a lowercase letter