How can I create JSON string from model data Swift?

Question

How can I create JSON string from other model data?

I am looking to create json string from data but not with success.

Results I am getting in array and then I have used For Loop to pass to AppointmentDownloadModel for json creation.

How can I pass data AppointmentDownloadModel and create JSON String.

Data Receiving Model:

struct ResponseData: Codable {

    let appointments : [Appointment]?
}


let decoder = JSONDecoder()
let response = try decoder.decode(ResponseData.self, from: result! as! Data)
self.appData = response.appointments
for everyApp in self.appData! {

}

Want to pass response data to this model:

struct AppointmentDownloadModel: Codable{
    var appointmentModel: Appointment
    var progress: Int = 0
    var failedList: [Int: String] = [:]
    var isFinished: Bool = false
}

Final need to create this string:

{"appointmentModel":{"appointmentHour":"12:00","backgroundColorDark":"#556f7b","backgroundColorLight":"#cfd8dc","controlHour":"","date":"2020-06-01T12:00:00","heatingType":"b","id":15469622,"isProjectManual":false,"projectFirmName":"Miray Doğalgaz (Erhan Şahin)","projectName":"KÖKSAL ÇOŞKUN-+D1+D3+D5","projectType":"k","subTitle":"18137 902179436-18137-408352"},"failedResourceList":[],"isFinished":false,"progress":0}

Answer 1

The following decodes the json example and create new AppointmentDownloadModel objects which are then encoded to Data (and converted to a string)

var models = [AppointmentDownloadModel]()

let decoder = JSONDecoder()
do {
    let response = try decoder.decode(ResponseData.self, from: data)
    if let appointments = response.appointments {
        models = appointments.map { AppointmentDownloadModel(appointmentModel: $0)}
    }
} catch {
    print(error)
}

let encoder = JSONEncoder()
do {
    let modelData = try encoder.encode(models)
    let jsonString = String(data: modelData, encoding: .utf8)
    print(jsonString)
} catch {
    print(error)
}