问使用无法解析的标识符'FIRAuth‘(Swift 2，Firebase 3.x)

EN

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)
}

}