How to store multiple back dates in a Swift Struct? - ios

Question

I would like to store the previous 4 days closing event in an individual struct so that i can make reference to them later on in the program. How would you go about storing the the closing event for each 4 days after sorting them from the JSON API.
The code below has sorted the previous 4 days but i am unable to figure how to store each day to use them separately
class DailyViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let jsonUrlString = "https://www.alphavantage.co/query?function=TIME_SERIES_DAILY&symbol=MSFT&apikey=demo"
let urlObj = URL(string: jsonUrlString)
URLSession.shared.dataTask(with: urlObj!) {(data, response, error) in
guard let data = data else { return }
do {
let forex = try JSONDecoder().decode(Root.self, from: data)
let sortedKeys = forex.timeSeriesDaily.keys.sorted(by: >)
let requestedKeys = sortedKeys.prefix(4)
var requestedPrices = [String:Forex]()
requestedKeys.forEach{ requestedPrices[$0] = forex.timeSeriesDaily[$0] }
print(requestedPrices)
print()
} catch {
print(error)
}
}.resume()
}
struct Root: Codable {
let metaData: [String: String]
let timeSeriesDaily: [String:Forex]
enum CodingKeys: String, CodingKey {
case timeSeriesDaily = "Time Series (Daily)"
case metaData = "Meta Data"
}
}
struct Forex: Codable {
let open, high, low, close: String
enum CodingKeys: String, CodingKey {
case open = "1. open"
case high = "2. high"
case low = "3. low"
case close = "4. close"
}
}
}

Answer 1

One way is to create a struct with four properties for this and add a specific init that takes an array
struct LastFour {
var close1: String
var close2: String
var close3: String
var close4: String
init?(_ closes: [String]) {
guard closes.count >= 4 else {
return nil
}
close1 = closes[0]
close2 = closes[1]
close3 = closes[2]
close4 = closes[3]
}
}
and then use map when initialising the struct from the dictionary
let lastFour = LastFour(requestedPrices.values.map {$0.close})
Note that the init is optional and returns nil in case the array is to short, another option could be to throw an error for instance.
Maybe a more flexible solution would be to use an array internally in the struct and then access the data via a method or perhaps computed properties
struct LastFour {
private var closeEvents: [String]
func close(at index: Int) -> String {
}
}
This would of course require similar code for init and checking the correct size but it would be easier to change if more or less elements are needed

Answer 2

My suggestion is to create another struct with the date and the close price
struct CloseData {
let date, price : String
}
and populate it
do {
let forex = try JSONDecoder().decode(Root.self, from: data)
let sortedKeys = forex.timeSeriesDaily.keys.sorted(by: >)
let requestedKeys = sortedKeys.prefix(4)
let requestedPrices = requestedKeys.map{ CloseData(date: $0, price: forex.timeSeriesDaily[$0]!.close) }
The result is an array of CloseData items