Will not show login page in swift

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iOS

Swift

hi my friends. this is my code for login page that work correctly:

func doLogin(username: String, password: String) {
        
        let parameters = [
            "NationalCode": username,
            "password": password
        ]
        let url = "http://home/login"
        Alamofire.request(url, method: .post, parameters: parameters, encoding: URLEncoding.httpBody).responseJSON { response in
            
            if let data = response.data {
                let json = String(data: data, encoding: String.Encoding.nonLossyASCII)
                if json=="0"{
                    let alert = UIAlertController(title: "error", message: "wronge username or password", preferredStyle: UIAlertControllerStyle.alert)
                    alert.addAction(UIAlertAction(title: "try", style: UIAlertActionStyle.cancel, handler: nil))
                    self.present(alert, animated: true, completion: nil)
                    return
                }
                else{
                    DispatchQueue.main.async(execute: { () -> Void in
                        self.performSegue(withIdentifier: "loginToMain", sender: self)
                    })
                    let jsonData = try? JSONSerialization.jsonObject(with: data, options: [])
                    guard let dictionary = jsonData as? [String:String] else { return }
                    print(dictionary["name"])
                }
            }
        }

when i click login button, i go to next page.
now how can i say the app do not show login page for next running until i log out??

(sorry i,m new in swift)

What I have tried:

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