iOS link two firebase accounts error - ios

Question

I'm trying to link two firebase accounts
a phone account ( signed in ) to Anonymous account ( prevUser )
this is my code
func verifyCode() {
let credential = PhoneAuthProvider.provider().credential(
withVerificationID: self.verificationID,
verificationCode: phoneCode.text!)
let prevUser = Auth.auth().currentUser!
Auth.auth().signIn(with: credential) { (user, error) in
if let error = error {
print("1 something went wrong : ", error.localizedDescription)
return
}
print("the user ID is : " , user!.uid)
prevUser.link(with: credential, completion: { (user, error) in
if let error = error {
print("something went wrong : ", error.localizedDescription)
return
}
})
}
}
I keep getting the same error always
something went wrong : The SMS code has expired. Please re-send the verification
code to try again.
thanks in advance

Answer 1

There are 2 issues here:
You are signing in with the phone auth credential first and then linking to the same credential which contains the same underlying SMS code which is a one time code. This will always fail with the error you are getting since the Firebase Auth backend can only use the code once (it immediately expires the first time it is used).
Even if the code is usable more than once, you can't have more than one user with the same phone credential. You first sign in one user with that credential and then try to link it to another user. This will always fail with an error that the credential already exists on another account.

Answer 2

Step 1: You can verify the phone number by providing phone number string and in completion you will be returned a verificationID and error if any.
func verifyPhoneNumber(withPhoneNo phoneNo:String, completion: #escaping (_ error: Error?, _ verificationID: String?)->Void) {
PhoneAuthProvider.provider().verifyPhoneNumber(phoneNo) { (verificationID, error) in
if let error = error {
print(error.localizedDescription)
completion(error, verificationID)
} else {
print(verificationID ?? "no id provided")
completion(nil, verificationID)
}
}
}
Step 2: Linking Phone Number to the current User by providing the current user, 6digit verification code, verificationID obtained from the previous function.
In completion you will be returned with an error if any.
func linkPhoneNumber(withUser user: User, verificationCode: String, verificationID id: String, completion: #escaping (_ error: Error?)-> Void) {
let credential = PhoneAuthProvider.provider().credential(withVerificationID: id, verificationCode: verificationCode)
user.link(with: credential) { (user, error) in
if let error = error {
print(error.localizedDescription)
completion(error)
} else {
print(user!.uid)
completion(nil)
}
}
}