AppDelegate.swift

import UIKit
import FacebookCore

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

  var window: UIWindow?


  public func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey : Any]? = nil) -> Bool {
    // Override point for customization after application launch.

     return SDKApplicationDelegate.shared.application(application, didFinishLaunchingWithOptions: launchOptions)
  }

    public func application(_ app: UIApplication, open url: URL, options: [UIApplicationOpenURLOptionsKey : Any] = [:]) -> Bool {
    return SDKApplicationDelegate.shared.application(app, open: url, options: options)
  }
  
  public func application(_ application: UIApplication, open url: URL, sourceApplication: String?, annotation: Any) -> Bool {
    return SDKApplicationDelegate.shared.application(application, open: url)
  }
}
}

ViewController.swift

import UIKit
import Alamofire
import FacebookCore
import FBSDKLoginKit

class LoginViewController: UIViewController {

 func getFBUserData(){
        if((FBSDKAccessToken.current()) != nil){
            FBSDKGraphRequest(graphPath: "me", parameters: ["fields": "id, name, first_name, last_name, picture.type(large), email"]).start(completionHandler: { (connection, result, error) -> Void in
                if (error == nil){
                    //everything works print the user data
                    print(result!)
                }
            })
        }
    }

 @IBAction func facebookLoginButtonPressed(_ sender: Any) {
        
        let fbLoginManager : FBSDKLoginManager = FBSDKLoginManager()
        fbLoginManager.logIn(withReadPermissions: ["email", "user_events", "user_likes", "user_birthday"], from: self) { (result, error) in
            if (error == nil){
                let fbloginresult : FBSDKLoginManagerLoginResult = result!
                if(fbloginresult.grantedPermissions.contains("email"))
                {
                    self.getFBUserData()
                }
            }
        }
    }
}