Authorization in Facebook, Swift 3, FBSDK

Question

I am trying to create an API for login user on facebook, but I have this error:

Thread 1:EXC_BAD_INSTRUCTION(code=EXC_I386_INVOP,subcode=0x0)

on this line:

self.accessToken = jsonData["access_token"].string!

Console shows:

My Code:

fatal error: unexpectedly found nil while unwrapping an Optional value (lldb)

func login(userType: String, completionHandler: @escaping (NSError?) -> Void) {

        let path = "api/social/convert-token/"
        let url = baseURL!.appendingPathComponent(path)
        let params: [String: Any] = [
            "grant_type": "convert_token",
            "client_id": CLIENT_ID,
            "client_secret": CLIENT_SECRET,
            "backend": "facebook",
            "token": FBSDKAccessToken.current().tokenString,
            "user_type": userType
        ]

        Alamofire.request(url!, method: .post, parameters: params, encoding: URLEncoding(), headers: nil).responseJSON { (response) in

            switch response.result {
            case .success(let value):

                let jsonData = JSON(value)

                self.accessToken = jsonData["access_token"].string!
                self.refreshToken = jsonData["refresh_token"].string!
                self.expired = Date().addingTimeInterval(TimeInterval(jsonData["expires_in"].int!))

                completionHandler(nil)
                break

            case .failure(let error):
                completionHandler(error as NSError?)
                break
            }
        }
    }

Answer 1

The problem was the app info in Constants.swift

let BASE_URL: String = ""
let CLIENT_ID: String = ""
let CLIENT_SECRET: String = ""