Tableview with JSON Data in Swift 4.2 - ios

Question

I'm new to Swift and I am at my wit's end, so please be kind to me.
I am building an app which downloads data from an url by posting a specific ID and getting back an JSON array. The JSON looks like this:
[{"group":"500","from":"2019-01-01","to":"2019-01-05"},{...}]
It has the group number as "group" and a start Date "from" and an end date "to".
I want to let the different groups shown in a Tableview with the From and To-Dates as well. I managed to download the data correctly but I failed by showing them in a tableview.
My code is down below. Maybe someone of you can find out what I've done wrong.
When I run the project I get an empty table.
import UIKit
typealias Fahrten = [FahrtenElement]
struct FahrtenElement: Codable {
let group: String?
let from: String?
let to: String?
enum CodingKeys: String, CodingKey {
case group = "group"
case from = "from"
case to = "to"
}
}
class BookingsController: UITableViewController {
var tableview: UITableView!
var groups = [Fahrten]()
// MARK: - Table view data source
override func viewDidLoad() {
super.viewDidLoad()
downloadData()
}
override func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
let label = UILabel()
label.text = "Groups"
label.backgroundColor = .yellow
return label
}
// Section
override func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.groups.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
//lblname to set the title from response
cell.textLabel?.text = "Group \(String(describing: groups[indexPath.row].group))"
cell.detailTextLabel?.text = "From \(String(describing: groups[indexPath.row].from)) to \(String(describing: groups[indexPath.row].to))"
return cell
}
func downloadData() {
let id = "..."
let url = URL(string: "...")!
// request url
var request = URLRequest(url: url)
// method to pass data POST - cause it is secured
request.httpMethod = "POST"
// body gonna be appended to url
let body = "id=(\(id))"
// append body to our request that gonna be sent
request.httpBody = body.data(using: .utf8)
URLSession.shared.dataTask(with: request) { (data, response, err) in
guard let data = data else { return }
do {
let groups = try JSONDecoder().decode(Fahrten.self, from: data)
print(groups)
self.tableview.reloadData() // I get an crash here: Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value }
} catch let jsonErr {
print("Error serializing json:", jsonErr)
}
}.resume()
}

Answer 1

From what I can see it looks like you are emptying the array and not reloading the data.
You should assign the resulting groups property to self.groups and then reload the data.
DispatchQueue.main.async {
self.groups = groups // change here
self.tableview.reloadData()
}

Answer 2

Try this code.
Your model.
typealias Fahrten = [FahrtenElement]
struct FahrtenElement: Codable {
let group: String
let from: String
let to: String
enum CodingKeys: String, CodingKey {
case group = "group"
case from = "from"
case to = "to"
}
}
Use it, I am using it with local json with same structure.
func getFehData(){
let url = Bundle.main.url(forResource: "fah", withExtension: "json")!
do {
let jsonData = try Data(contentsOf: url)
let fahrten = try? JSONDecoder().decode(Fahrten.self, from: jsonData)
print(fahrten)
}
catch {
print(error)
}
}
Output : (Dummy data)