Use of unresolved identifier 'FIRAuth' (Swift 2, Firebase 3.x)
<p>Updating to the new firebase. Created a new signin VC and everything was working fine in terms of no errors.</p>

<p>Trying to replicate this new tutorial: <a href="https://codelabs.developers.google.com/codelabs/firebase-ios-swift/index.html?index=..%2F..%2Findex#0" rel="noreferrer">https://codelabs.developers.google.com/codelabs/firebase-ios-swift/index.html?index=..%2F..%2Findex#0</a> </p>

<p>Now all of a sudden I'm getting the error Use of unresolved identifier 'FIRAuth' all over my VC. </p>

<p>I've tried re-installing the pods file and haven't had any luck, it seems that sometimes if it add "import Firebase" then remove it the app will compile, it seems there is no rhyme or reason for why it works sometimes and other times it doesn't:</p>

<p>Here's my code: </p>

<pre><code>import UIKit
import FirebaseAuth


class SignInViewController: UIViewController {

@IBOutlet weak var emailField: UITextField!

@IBOutlet weak var passwordField: UITextField!

override func viewDidAppear(animated: Bool) {
    if let user = FIRAuth.auth()?.currentUser { //error here 
        self.signedIn(user)
    }
}

@IBAction func didTapSignIn(sender: AnyObject) {
    // Sign In with credentials.
    let email = emailField.text
    let password = passwordField.text
    FIRAuth.auth()?.signInWithEmail(email!, password: password!) { //error here (user, error) in
        if let error = error {
            print(error.localizedDescription)
            return
        }
        self.signedIn(user!)
    }
}
@IBAction func didTapSignUp(sender: AnyObject) {
    let email = emailField.text
    let password = passwordField.text
    FIRAuth.auth()?.createUserWithEmail(email!, password: password!) { // error here(user, error) in
        if let error = error {
            print(error.localizedDescription)
            return
        }
        self.setDisplayName(user!)
    }
}

func setDisplayName(user: FIRUser) {
    let changeRequest = user.profileChangeRequest()
    changeRequest.displayName = user.email!.componentsSeparatedByString("@")[0]
    changeRequest.commitChangesWithCompletion(){ (error) in
        if let error = error {
            print(error.localizedDescription)
            return
        }
        self.signedIn(FIRAuth.auth()?.currentUser) //error here
    }
}

@IBAction func didRequestPasswordReset(sender: AnyObject) {
    let prompt = UIAlertController.init(title: nil, message: "Email:", preferredStyle: UIAlertControllerStyle.Alert)
    let okAction = UIAlertAction.init(title: "OK", style: UIAlertActionStyle.Default) { (action) in
        let userInput = prompt.textFields![0].text
        if (userInput!.isEmpty) {
            return
        }
        FIRAuth.auth()?.sendPasswordResetWithEmail(userInput!) { //error here (error) in
            if let error = error {
                print(error.localizedDescription)
                return
            }
        }
    }
    prompt.addTextFieldWithConfigurationHandler(nil)
    prompt.addAction(okAction)
    presentViewController(prompt, animated: true, completion: nil);
}

func signedIn(user: FIRUser?) {
    MeasurementHelper.sendLoginEvent()

    AppState.sharedInstance.displayName = user?.displayName ?? user?.email
    AppState.sharedInstance.photoUrl = user?.photoURL
    AppState.sharedInstance.signedIn = true
    NSNotificationCenter.defaultCenter().postNotificationName(Constants.NotificationKeys.SignedIn, object: nil, userInfo: nil)
   // performSegueWithIdentifier(Constants.Segues.SignInToFp, sender: nil)
}

}
</code></pre>

<p>Does anyone have any idea why this would be happening? </p>