SWIFT: Error EXC_BAD_INSTRUCTION

Question

the following error appears after running my app and trying to register an user:

Thread 1: EXC_BAD_INSTRUCTION (code=EXC_l386_INVOP,s subcode=0x0)

This appears at the end of the code:

} as! (Data?, URLResponse?, Error?) -> Void )

  let myUrl = NSURL(string: "http://127.0.0.1/MySQL_PHP/userRegister.php")
        var request = URLRequest(url: myUrl as! URL)
        request.httpMethod = "POST"
      //  let config = URLSessionConfiguration.default
        let session = URLSession.shared

        let postString = "email=\(userEmail)&passwort=\(userPasswort)&vorname=\(userVorname)&nachname=\(userName)&benutzer=\(userBenutzer)"
        request.httpBody = postString.data(using: String.Encoding.utf8)



        let task = session.dataTask(with: request, completionHandler: { (data: Data?, response: URLResponse?, error: Error?) in
            if error != nil {
                print("error=\(error)")
                return
            }



            var err: NSError?
            var json = try JSONSerialization.jsonObject(with: data!, options: []) as? NSDictionary

            if let parseJSON = json {
                var resultValue = parseJSON["status"] as? String
                print("result: \(resultValue)")

                var isUserRegistered: Bool = false
                if (resultValue == "Success") {
                    isUserRegistered = true
                }

                var messageToDisplay: String = parseJSON["message"] as! String!
                if (!isUserRegistered){
                    messageToDisplay = parseJSON["message"] as! String!
                }
                DispatchQueue.main.async(execute:  {

                    var myAlert = UIAlertController(title:"Alert", message: messageToDisplay, preferredStyle: UIAlertControllerStyle.alert)

                    let okAction = UIAlertAction(title: "Ok", style: UIAlertActionStyle.default){
                        action in
                        self.dismiss(animated: true, completion: nil)
                    }
                    myAlert.addAction(okAction)
                    self.present(myAlert, animated: true, completion: nil)

                })
            }
        } as! (Data?, URLResponse?, Error?) -> Void )

        task.resume()

Answer 1

The error is misleading. It's not directly related to the data task closure.

First of all do not cast at all

let task = session.dataTask(with: request, completionHandler: { (data, response, error) in

...

})

or even still shorter using trailing closure syntax:

let task = session.dataTask(with: request) { (data, response, error) in

...

}

The error occurs because the do - catch block is missing around try JSONSerialization

The error goes away either by adding the do - catch block or using try!

And finally a suggestion: Please, please, please do not use NSArray / NSDictionary in Swift. You are fighting the strong type system.