Swift - How to extract all values with same key names - json

Question

having looked at several posts I didn't find what I was looking for. I hope this post will help me.
I use the api of CoinDesk, what I'm trying to do now is to retrieve in the answer all the codes (EUR, USD, GBP) but I can't get all the assets.
{
"time": {
"updated": "Feb 20, 2021 19:48:00 UTC",
"updatedISO": "2021-02-20T19:48:00+00:00",
"updateduk": "Feb 20, 2021 at 19:48 GMT"
},
"disclaimer": "This data was produced from the CoinDesk Bitcoin Price Index (USD). Non-USD currency data converted using hourly conversion rate from openexchangerates.org",
"chartName": "Bitcoin",
"bpi": {
"USD": {
"code": "USD",
"symbol": "$",
"rate": "57,014.5954",
"description": "United States Dollar",
"rate_float": 57014.5954
},
"GBP": {
"code": "GBP",
"symbol": "£",
"rate": "40,681.1111",
"description": "British Pound Sterling",
"rate_float": 40681.1111
},
"EUR": {
"code": "EUR",
"symbol": "€",
"rate": "47,048.5582",
"description": "Euro",
"rate_float": 47048.5582
}
}
}
here's how I'm going to get the data
public class NetworkManager {
static public func fetchBPI() {
let url = "https://api.coindesk.com/v1/bpi/currentprice.json"
Alamofire.request(url).responseJSON { response in
switch response.result {
case .success:
print("✅ Success ✅")
if let json = response.data {
do {
let data = try JSON(data: json)
print(data)
let context = PersistentContainer.context
let entity = NSEntityDescription.entity(forEntityName: "BPI", in: context)
let newObject = NSManagedObject(entity: entity!, insertInto: context)
//Date Formatter
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "MM-dd-yyyy HH:mm"
let date = dateFormatter.date(from: data["time"]["updated"].rawValue as! String)
dateFormatter.timeZone = NSTimeZone.local
let timeStamp = dateFormatter.string(from: date ?? Date())
newObject.setValue(timeStamp, forKey: "time")
newObject.setValue(data["chartName"].rawValue, forKey: "chartName")
newObject.setValue(data["bpi"]["EUR"]["symbol"].rawValue, forKey: "symbol")
newObject.setValue(data["bpi"]["EUR"]["rate"].rawValue, forKey: "rate")
newObject.setValue(data["bpi"]["EUR"]["code"].rawValue, forKey: "code")
do {
try context.save()
print("✅ Data saved ✅")
} catch let error {
print(error)
print("❌ Saving Failed ❌")
}
}
catch {
print("❌ Error ❌")
}
}
case .failure(let error):
print(error)
}
}
}
}
I would like to get in the bpi key all the codes and put them in a list to use them.

Answer 1

The best way to handle the json here in my opinion is to treat the content under "bpi" as a dictionary instead.
struct CoinData: Codable {
let time: Time
let chartName: String
let bpi: [String: BPI]
}
struct BPI: Codable {
let code: String
let rate: Double
enum CodingKeys: String, CodingKey {
case code
case rate = "rate_float"
}
}
struct Time: Codable {
let updated: Date
enum CodingKeys: String, CodingKey {
case updated = "updatedISO"
}
}
I have removed some unnecessary (?) properties and also note that I made updatedISO in Time into a Date if that might be useful since it's so easy to convert it.
To properly decode this use try with a do/catch so you handle errors properly.
Here is an example of that where I also loop over the different currencies/rates
do {
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601
let result = try decoder.decode(CoinData.self, from: data)
print(result.time.updated)
let coins = result.bpi.values
for coin in coins {
print(coin)
}
} catch {
print(error)
}
Output:
2021-02-20 19:48:00 +0000
BPI(code: "GBP", rate: 40681.1111)
BPI(code: "USD", rate: 57014.5954)
BPI(code: "EUR", rate: 47048.5582)

Answer 2

You should use objects to represent the data from the server. It would be something like this:
struct CoinData: Codable {
let time: Time
let disclaimer, chartName: String
let bpi: BPI
}
struct BPI: Codable {
let usd, gbp, eur: Eur
enum CodingKeys: String, CodingKey {
case usd = "USD"
case gbp = "GBP"
case eur = "EUR"
}
}
struct Eur: Codable {
let code, symbol, rate, eurDescription: String
let rateFloat: Double
enum CodingKeys: String, CodingKey {
case code, symbol, rate
case eurDescription = "description"
case rateFloat = "rate_float"
}
}
struct Time: Codable {
let updated: String
let updatedISO: String
let updateduk: String
}
Than when you download the data you parse it like this:
let coinData = try? JSONDecoder().decode(CoinData.self, from: jsonData)
coinData?.bpi.eur // Access EUR for instance
UPDATE:
Simple demo to demonstrate the parsing using the data you get from your server:
let dataFromServer = "{\"time\":{\"updated\":\"Feb 20, 2021 21:02:00 UTC\",\"updatedISO\":\"2021-02-20T21:02:00+00:00\",\"updateduk\":\"Feb 20, 2021 at 21:02 GMT\"},\"disclaimer\":\"This data was produced from the CoinDesk Bitcoin Price Index (USD). Non-USD currency data converted using hourly conversion rate from openexchangerates.org\",\"chartName\":\"Bitcoin\",\"bpi\":{\"USD\":{\"code\":\"USD\",\"symbol\":\"$\",\"rate\":\"56,689.8367\",\"description\":\"United States Dollar\",\"rate_float\":56689.8367},\"GBP\":{\"code\":\"GBP\",\"symbol\":\"£\",\"rate\":\"40,449.3889\",\"description\":\"British Pound Sterling\",\"rate_float\":40449.3889},\"EUR\":{\"code\":\"EUR\",\"symbol\":\"€\",\"rate\":\"46,780.5666\",\"description\":\"Euro\",\"rate_float\":46780.5666}}}"
do {
let json = try JSONDecoder().decode(CoinData.self, from: dataFromServer.data(using: .utf8)!)
print(json.bpi.eur) // Will print EUR object
} catch let error {
print(error)
}