Parsing JSON data to fill a TableView

Question

I've a JSON (for now in local), that I want to parse to put these data in a listView.

I've already created the view and tried a few things (like this tutorial : https://www.journaldev.com/21839/ios-swift-json-parsing-tutorial) to parse that JSON, with no success.

Here is some code I tried :

class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

@IBOutlet weak var labelHeader: UILabel!
@IBOutlet weak var tableView: UITableView!

var channelList = [channelData]()

override func viewDidLoad() {
    super.viewDidLoad()
let url = Bundle.main.url(forResource: "channels", withExtension: "json")

    guard let jsonData = url
        else{
            print("data not found")
            return
    }

    guard let data = try? Data(contentsOf: jsonData) else { return }

    guard let json = try? JSONSerialization.jsonObject(with: data, options: []) else{return}

    if let dictionary = json as? [String: Any] {

        if let title = dictionary["title"] as? String {
            print("in title")
            labelHeader.text = title
        }

        if let data = dictionary["data"] as? Any {
            print("data is \(data)")
        }
        if let date = dictionary["date"] as? Date {
            print("date is \(date)")
        }
        // And so on

        for (key, value) in dictionary {
            print("Key is: \(key) and value is \(value)" )
            //This print the whole JSON to the console.
        }
    }

    //Now lets populate our TableView
    let newUrl = Bundle.main.url(forResource: "channels", withExtension: "json")

    guard let j = newUrl
        else{
            print("data not found")
            return
    }

    guard let d = try? Data(contentsOf: j)
        else { print("failed")
            return
    }

    guard let rootJSON = try? JSONSerialization.jsonObject(with: d, options: [])
        else{ print("failedh")
            return
    }

    if let JSON = rootJSON as? [String: Any] {
        labelHeader.text = JSON["id"] as? String //Should update the Label in the ListView with the ID found in the JSON

        guard let jsonArray = JSON["type"] as? [[String: Any]] else {
            return
        }

        let name = jsonArray[0]["name"] as? String
        print(name ?? "NA")
        print(jsonArray.last!["date"] as? Int ?? 1970)

        channelList = jsonArray.compactMap{return channelData($0)}

        self.tableView.reloadData()

    }
}

Here is a sample of the JSON file :

{
"format": "json",
"data": [
    {
        "type": "channel",
        "id": "123",
        "updated_at": "2019-05-03 11:32:57",
        "context": "search",
        "relationships": {
            "recipients": [
                {
                    "type": "user",
                    "id": 321,
                    "participant_id": 456
                }
            ],
            "search": {
                "type": "search",
                "title": "Title"
            },
        }
    },

I'd like to find the best way to work with kind of this JSON.

For now I'm not able to get the data to the listView. The most I have is my JSON in the console of xCode (at least it means I'm able to open the JSON).

Answer 1

Please use this as your base code on your current development. I've made use of Structs that will help you keep an order on your JSON model aswell encode it properly and use it as an object somewhere in the future.

STRUCTS

// http request response results iTunes Site.
struct SearchResult: Decodable {
    let resultCount: Int
    let results: [Result]
}

// Raw Result
struct Result: Decodable {
    let trackId: Int
    let artistId: Int
    let artistName: String
    let collectionName: String
    let trackName: String
    let artworkUrl30: String
    let artworkUrl60: String
    let artworkUrl100: String
    let primaryGenreName: String
    let trackPrice: Float
    let collectionPrice: Float
    let trackTimeMillis: Int

}

FUNCTION CODE

func fetchArtists(searchTerm: String, completion: @escaping (SearchResult?, Error?) -> ()) {
        let escapedString = searchTerm.addingPercentEncoding(withAllowedCharacters: .urlHostAllowed)!
        let urlString = "https://itunes.apple.com/search?term=\(escapedString)&entity=musicTrack"
        fetchGenericJSONData(urlString: urlString, completion: completion)
    }

    func fetchGenericJSONData<T: Decodable>(urlString: String, completion: @escaping (T?, Error?) -> ()) {

        guard let url = URL(string: urlString) else { return }
        URLSession.shared.dataTask(with: url) { (data, resp, err) in
            if let err = err {
                completion(nil, err)
                return
            }
            do {
                let objects = try JSONDecoder().decode(T.self, from: data!)
                completion(objects, nil)
            } catch {
                completion(nil, error)
            }
            }.resume()
    }

REQUEST CODE HOW TO USE IT.

fetchArtists(searchTerm: searchText) { res, err in
    if let err = err {
        print("Failed to fetch artists:", err)
        return
    }
    self.iTunesResults = res?.results ?? []
    print(self.iTunesResults.artistName)
    // Uncomment this in case you have a tableview to refresh
    // DispatchQueue.main.async {
    //     self.tableView.reloadData()
    // }
}

Answer 2

The recommended way to parse JSON in Swift 4+ is the Codable protocol.

Create the structs

struct Root: Decodable {
    let format: String
    let data: [ChannelData]
}

struct ChannelData: Decodable {
    let type, id, updatedAt, context: String
    let relationships: Relationships
}

struct Relationships: Decodable {
    let recipients: [Recipient]
    let search: Search
}

struct Recipient: Decodable {
    let type: String
    let id: Int
    let participantId: Int
}

struct Search: Decodable {
    let type: String
    let title: String
}

As the channels.json file is in the application bundle and cannot be modified you can reduce viewDidLoad to

var channelList = [ChannelData]()

override func viewDidLoad() {
    super.viewDidLoad()
    let url = Bundle.main.url(forResource: "channels", withExtension: "json")!
    let data = try! Data(contentsOf: url)
    let decoder = JSONDecoder()
    decoder.keyDecodingStrategy = .convertFromSnakeCase
    let result = try! decoder.decode(Root.self, from: data)
    channelList = result.data
    self.tableView.reloadData()
}

If the code crashes it reveals a design mistake. The structs match the JSON in the question. Probably it's much larger, then you must adjust or extend the structs.