Swift / Firebase : Facebook 사용자가 계정을 만들 때 Firebase 데이터베이스에 제대로 저장하려면 어떻게해야합니까?

완료 블록 graphRequest.startWithCompletionHandler이 실행될 때만 값을 업데이트해야합니다. 그 때가 Facebook!에서 데이터를 가져 오기 때문입니다. 완료 블록 usersReference.updateChildValues안에 있어야합니다 graphRequest.startWithCompletionHandler({ (connection, result, error) -> Void in. 아래에 첨부했습니다. 시도 해봐!!

func showLoginView() {
    let loginManager = FBSDKLoginManager()
    loginManager.logInWithReadPermissions(fbPermissions, fromViewController: self, handler: { (result:FBSDKLoginManagerLoginResult!, error:NSError!) -> Void in

        if ((error) != nil) {
            print("Error loggin in is \(error)")
        } else if (result.isCancelled) {
            print("The user cancelled loggin in")
        } else {
            // No error, No cancelling:
            // using the FBAccessToken, we get a Firebase token
            let credential = FIRFacebookAuthProvider.credentialWithAccessToken(FBSDKAccessToken.currentAccessToken().tokenString)

            // using the credentials above, sign in to firebase to create a user session
            FIRAuth.auth()?.signInWithCredential(credential) { (user, error) in
                print("User logged in the firebase")

                // adding a reference to our firebase database
                let ref = FIRDatabase.database().referenceFromURL("https://project-12345.firebaseio.com/")

                // guard for user id
                guard let uid = user?.uid else {
                    return
                }

                // create a child reference - uid will let us wrap each users data in a unique user id for later reference
                let usersReference = ref.child("users").child(uid)

                // performing the Facebook graph request to get the user data that just logged in so we can assign this stuff to our Firebase database:
                let graphRequest : FBSDKGraphRequest = FBSDKGraphRequest(graphPath: "me", parameters: ["fields": "id, name, email"])
                graphRequest.startWithCompletionHandler({ (connection, result, error) -> Void in

                    if ((error) != nil) {
                        // Process error
                        print("Error: \(error)")
                    } else {
                        print("fetched user: \(result)")

                        // Facebook users name:
                        let userName:NSString = result.valueForKey("name") as! NSString
                        self.usersName = userName
                        print("User Name is: \(userName)")
                        print("self.usersName is \(self.usersName)")

                        // Facebook users email:
                        let userEmail:NSString = result.valueForKey("email") as! NSString
                        self.usersEmail = userEmail
                        print("User Email is: \(userEmail)")
                        print("self.usersEmail is \(self.usersEmail)")

                        // Facebook users ID:
                        let userID:NSString = result.valueForKey("id") as! NSString
                        self.usersFacebookID = userID
                        print("Users Facebook ID is: \(userID)")
                        print("self.usersFacebookID is \(self.usersFacebookID)")

                        //graphRequest.startWithCompletionHandler may not come back during serial
                        //execution so you cannot assume that you will have date by the time it gets
                        //to the let values = ["name":
                        //By putting it inside here it makes sure to update the date once it is
                        //returned from the completionHandler
                        // set values for assignment in our Firebase database
                        let values = ["name": self.usersName, "email": self.usersEmail, "facebookID": self.usersFacebookID]

                        // update our databse by using the child database reference above called usersReference
                        usersReference.updateChildValues(values, withCompletionBlock: { (err, ref) in
                            // if there's an error in saving to our firebase database
                            if err != nil {
                                print(err)
                                return
                            }
                            // no error, so it means we've saved the user into our firebase database successfully
                            print("Save the user successfully into Firebase database")
                        })
                    }
                })


            }
        }
    })
}