TwitterLogin.swift

class func signInWithTwitter() {
        
        Twitter.sharedInstance().logIn(withMethods: .webBased) { (session, error) in
          if error != nil {
                print(error?.localizedDescription)
            }else{
            if session != nil {
                if let unwrappedSession = session {
                    let token = unwrappedSession.authToken
                    let secret = unwrappedSession.authTokenSecret
                    let credentials = FIRTwitterAuthProvider.credential(withToken: token, secret: secret)
                    FIRAuth.auth()?.signIn(with: credentials, completion: { (user, error) in
                        if let error = error {
                            print(error.localizedDescription)
                            let alert = UIAlertController(title: "error", message: "\(error.localizedDescription)", preferredStyle: .alert)
                            let okAction = UIAlertAction(title: "Ok", style: .default, handler: nil)
                            alert.addAction(okAction)
                        }else{
                            
                            DispatchQueue.main.async {
                                    NotificationCenter.default.post(name: .closeLoginVC, object: nil)
                            }
                            
                        }
                        
                    })
                }
            }
        }
        }
    }