How to check if email already exist before creating an account (Swift) - swift

Question

I know different variations of this question have been asked. However I seem to keep running into the same issue every time.
I want to check if an email already exist before the user pushes onto the next view. I will enter an email that exist in the database and the performSegue func is always called and pushes the user as if that email does not exist.
The only way I can check officially is when the user reaches the final sign up VC and the Auth.auth().createUser(withEmail: email as! String, password: password as! String ) { (user, error) in code will check for all errors.
However for good user experience I would hate for the user to have to click back three times to change the email address. Here is the code I have for the enter email view controller.
// Check if email is already taken
Auth.auth().fetchSignInMethods(forEmail: emailTextField.text!, completion: { (forEmail, error) in
// stop activity indicator
self.nextButton.setTitle("Continue", for: .normal)
self.activityIndicator.stopAnimating()
if let error = error {
print("Email Error: \(error.localizedDescription)")
print(error._code)
self.handleError(error)
return
} else {
print("Email is good")
self.performSegue(withIdentifier: "goToCreateUsernameVC", sender: self)
}
})
First off am I even entering the create property in the forEmail section? I added emailTextField.text because its the only way I know how even get the email the user typed. Does anyone know a better way I can do this?

Answer 1

How I create user accounts
This is an example of what I use. When a user provides credentials, FirebaseAuth checks if these credentials can be used to make a user account. The function returns two values, a boolean indicating whether the creation was successful, and an optional error, which is returned when the creation is unsuccessful. If the boolean returns true, we simply push to the next view controller. Otherwise, we present the error.
func createUserAcct(completion: #escaping (Bool, Error?) -> Void) {
//Try to create an account with the given credentials
Auth.auth().createUser(withEmail: emailTextField.text!, password: passwordConfirmTextField.text!) { (user, error) in
if error == nil {
//If the account is created without an error, then we will make a ProfileChangeRequest, i.e. update the user's photo and display name.
if let firebaseUser = Auth.auth().currentUser {
let changeRequest = firebaseUser.createProfileChangeRequest()
//If you have a URL for FirebaseStorage where the user has uploaded a profile picture, you'll pass the url here
changeRequest.photoURL = URL(string: "nil")
changeRequest.displayName = self.nameTextField.text!
changeRequest.commitChanges { error in
if let error = error {
// An error happened.
completion(false, error)
} else {
//If the change is committed successfully, then I create an object from the credentials. I store this object both on the FirebaseDatabase (so it is accessible by other users) and in my user defaults (so that the user doesn't have to remotely grab their own info
//Create the object
let userData = ["email" : self.emailTextField.text!,"name": self.nameTextField.text!] as [String : Any]
//Store the object in FirebaseDatabase
Database.database().reference().child("Users").child(firebaseUser.uid).updateChildvalues(userData)
//Store the object as data in my user defaults
let data = NSKeyedArchiver.archivedData(withRootObject: userData)
UserDefaults.standard.set(data, forKey: "UserData")
UserDefaults.standard.set([Data](), forKey: "UserPhotos")
completion(true, nil)
}
}
}
} else {
// An error happened.
completion(false, error)
}
}
}
Here is an example of how I would use it. We can use the success boolean returned to determine if we should push to the next view controller, or present an error alert to the user.
createUserAcct { success, error in
//Handle the success
if success {
//Instantiate nextViewController
let storyboard = UIStoryboard(name: "Main", bundle: .main)
let nextVC = storyboard.instantiateViewController(withIdentifier: "NextVC") as! NextViewController
//Push typeSelectVC
self.navigationController!.pushViewController(viewController: nextVC, animated: true, completion: {
//We are no longer doing asynchronous work, so we hide our activity indicator
self.activityIndicator.isHidden = true
self.activityIndicator.stopAnimating()
})
} else {
//We now handle the error
//We are no longer doing asynchronous work, so we hide our activity indicator
self.activityIndicator.isHidden = true
self.activityIndicator.stopAnimating()
//Create a UIAlertController with the error received as the message (ex. "A user with this email already exists.")
let alertController = UIAlertController(title: "Error", message: error!.localizedDescription, style: .alert)
let ok = UIAlertAction(title: "OK", style: .cancel, action: nil)
//Present the UIAlertController
alertController.addAction(ok)
self.present(alertController, animated: true, completion: nil)
}
}
Let me know if this all makes sense, I know there is a lot to it. I'm just considering things you'll maybe find you need done anyways that you may not be aware of (like making change requests, or storing a data object on FirebaseDatabase).
Now for checking if the email is already taken:
Remember when I said that I post a user object to FirebaseDatabase upon account creation? Well we can query for the given email to see if it already exists. If it doesn't we continue with the flow as normal, without having actually created the account. Otherwise, we simply tell the user to pick another email address.
Pushing a user object to your database (taken from the above code):
if let firebaseUser = Auth.auth().currentUser {
//Create the object
let userData = ["email" : self.emailTextField.text!,"name": self.nameTextField.text!] as [String : Any]
//Store the object in FirebaseDatabase
Database.database().reference().child("Users").child(firebaseUser.uid).updateChildvalues(userData)
}
And now querying to see if somebody already has that email:
func checkIfEmailExists(email: String, completion: #escaping (Bool) -> Void ) {
Database.database().reference().child("Users").queryOrdered(byChild: "email").queryEqual(toValue: email).observeSingleEvent(of: .value, with: {(snapshot: DataSnapshot) in
if let result = snapshot.value as? [String:[String:Any]] {
completion(true)
} else {
completion(false)
}
}
}
Then we can call this like so:
checkIfEmailExists(email: emailTextField.text!, completion: {(exists) in
if exists {
//Present error that the email is already used
} else {
//Segue to next view controller
}
})