Getting error in json decode

First of all, your JSON FROM SERVER represents a single JSON object, which is outlined as follows:

{
    "message": "Student Found",
    "student": {
        ...
    }
}

It has two key-value pairs, one "message" with a JSON string, another "student" with a JSON object.

If you want to represent it as a Decodable Swift struct, you need two properties, but your `StudentLogin` has no properties.

You may need something like this:

struct StudentLogin: Decodable {
    var message: String
    var student: Student
}

With Student defined as:

struct Student: Decodable {
    var studentID: String
    var name: String
    var phone: String
    var email: String
    var specialisation: String
    var yearOfJoining: String
    var keyCode: String
    var schoolID: String
    var registrationID: String
    var batchID: String
    var usingOS: String
    var loginID: String
    var course: String
    var macID: String
    var bulkUpload: String? //<- can be null
    var createdBy: String
    var createdOn: Date
    var updatedBy: String
    var updatedOn: Date
    var address: String
    var gender: String
    var status: Int //<- JSON number
}

Better modify your deserializing code like this to clarify what may cause problem:

        do {
            guard let data = data else {
                print("data is nil")
                return
            }
            let responseJSON = try JSONSerialization.jsonObject(with: data)
            if let response = responseJSON as? [String: Any], response.count == 2 {
                self.parseJSON(data: data)
                print(self.studentdata)
            } else {
                print("response was not a JSON object")
                //...
            }
        } catch {
            print(error)
            //...
        }

The response is not a JSON array, so the result type should not be an Array type like `[StudentLogin]`.

And the date format in you JSON cannot be recognized as `Date` with `JSONDecoder`.

So your `parseJSON` would look like this:

    var studentdata: [StudentLogin] = [] //<- I guessed your `studentdata` is an Array of `StudentLogin`
    func parseJSON(data: Data) {
        do {
            let decoder = JSONDecoder()
            let dateFormatter = DateFormatter()
            dateFormatter.timeZone = TimeZone.current //<- You may need to change this
            dateFormatter.locale = Locale(identifier: "en_US_POSIX")
            dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
            decoder.dateDecodingStrategy = .formatted(dateFormatter)
            let studentFound = try decoder.decode(StudentLogin.self, from: data) //<- Not `[StudentLogin].self`
            self.studentdata = [studentFound]
        } catch let error {
            print(error)
        }
    }

The code above would not work becaused I needed to fill many parts by guess. You should better include all relevant info and error messages.