Not finding usernames already in the Firebase Database with Swift - ios

Question

I am trying to check my Firebase database to see if there is already a username taken within the database. Unfortunately, when I use a username which is already saved in there, it doesn't let me know. Code below.
#objc func pushedToRegister(_ sender: SignInSignUpButtons) {
checkUserNameAlreadyExist()
Auth.auth().createUser(withEmail: email.text!, password: password.text!, completion: { (user, error) in
if error != nil {
self.errorMessage = (error?.localizedDescription)!
print(error!)
self.showErrorView(forReason: 0)
return
}
else {
print("Registration was successful!")
//Here we should go back to the home screen where the message at the top should say welcome back USER!
if let userID = user?.user.uid {
//Create User Profile
let databaseRef = Database.database().reference()
let usersRef = databaseRef.child("Users").child(userID)
let usernameValue = ["username":self.username.text]
usersRef.updateChildValues(usernameValue, withCompletionBlock: { (err, ref) in
if err != nil {
print(err!.localizedDescription)
self.showErrorView(forReason: 2)
return
}
//Profile created and updated!
self.navigationController?.popViewController(animated: true)
})
}
}
})
}
func checkUserNameAlreadyExist() {
let ref = Database.database().reference()
var usernameTaken = false
ref.child("Users").queryOrdered(byChild: "username").queryEqual(toValue: username.text!).observeSingleEvent(of: .value, with: { snapshot in
if snapshot.exists(){
usernameTaken = true
print("username taken")
}else{
usernameTaken = false
print("username available")
}
}) { error in
print(error.localizedDescription)
}
if usernameTaken == false{
//do stuff with unique username
}
}
Unfortunately, every time I type in the same username, it lets me create a new profile everytime. It does not alert me to the fact that the username is already taken.

Answer 1

Firebase functions are asynchronous, so they do not block the rest of the code from running. If you want your code to wait for a function to complete, one option is use closures. You can check out my blog post on closures to see some examples.
Also, the code shown doesn't actually do anything to prevent the rest of the function from running. You need to write some sort of condition to handle that. For example, you could use a boolean in your completion handler, like this:
func checkUserNameAlreadyExist(completion: #escaping (Bool) -> Void) {
let ref = Database.database().reference()
ref.child("Users").queryOrdered(byChild: "username").queryEqual(toValue: username.text!).observeSingleEvent(of: .value, with: { snapshot in
if snapshot.exists() {
usernameTaken = true
print("username taken")
completion(true)
} else {
usernameTaken = false
print("username available")
completion(false)
}
}) { error in
print(error.localizedDescription)
completion(true)
}
}
Then in pushToRegister, you check if the boolean is true before proceeding.
#objc func pushedToRegister(_ sender: SignInSignUpButtons) {
checkUserNameAlreadyExist() { isTaken in
if (isTaken == true) {
// show some message to the user
return
}
Auth.auth().createUser(withEmail: email.text!, password: password.text!, completion: { (user, error) in
if let error = error {
self.errorMessage = error.localizedDescription
print(error)
self.showErrorView(forReason: 0)
return
}
print("Registration was successful!")
//Here we should go back to the home screen where the message at the top should say welcome back USER!
if let userID = user?.user.uid {
//Create User Profile
let databaseRef = Database.database().reference()
let usersRef = databaseRef.child("Users").child(userID)
let usernameValue = ["username":self.username.text]
usersRef.updateChildValues(usernameValue, withCompletionBlock: { (err, ref) in
if let err = err {
print(err.localizedDescription)
self.showErrorView(forReason: 2)
return
}
//Profile created and updated!
self.navigationController?.popViewController(animated: true)
})
}
})
}
}