Firebase Facebook login check if user exist
<p>I have an facebook login system which works with firebase but I want to check if user exist on my firebase (i don't want to add it, just want to make sure if he exist because I want to redirect user to another page to complete its profile, once its done I'll want to send it to firebase).</p>

<p>I just need to check if user exist on my db. Here is the code that I try but it returns nil error and it automatically add user to firebase.</p>

<pre><code>let credential = FIRFacebookAuthProvider.credentialWithAccessToken(FBSDKAccessToken.currentAccessToken().tokenString)


FIRAuth.auth()?.signInWithCredential(credential) { (user, error) in
        // ... 

}
</code></pre>