LoginViewController.swift

@IBAction func btnLoginWithFacebookClicked(_ sender: Any) {
    let fbLoginManager:FBSDKLoginManager = FBSDKLoginManager()
    fbLoginManager.logIn(withReadPermissions: ["email"], from: self) {(result, error) in
        if (error == nil){
            let fbLoginResult:FBSDKLoginManagerLoginResult = result!
            if fbLoginResult.grantedPermissions != nil {
                if(fbLoginResult.grantedPermissions.contains("email")) {
                    self.getFBUserData()
                    self.turnToIndexSreen()
                    //fbLoginManager.logOut()
                }

            }
        }
    }
}