Exchange Rate Key Value Lookup With Weird JSON File Format - swiftui

Question

I need help with currency exchange rate lookup given a key (3 digit currency code). The JSON object is rather unusual with no lablels such as date, timestamp, success, or rate. The first string value is the base or home currency. In the example below it is "usd" (US dollars).
I would like to cycle through all the currencies to get each exchange rate by giving its 3 digit currency code and storing it in an ordered array.
{
"usd": {
"aed": 4.420217,
"afn": 93.3213,
"all": 123.104693,
"amd": 628.026474,
"ang": 2.159569,
"aoa": 791.552347,
"ars": 111.887966,
"aud": 1.558363,
"awg": 2.164862,
"azn": 2.045728,
"bam": 1.9541,
"bbd": 2.429065,
"bch": 0.001278
}
}
In a slightly different formatted JSON object I used the following loop to copy exchange rates to an ordered array.
for index in 0..<userData.rateArray.count {
currencyCode = currCode[index]
if let unwrapped = results.rates[currencyCode] {
userData.rateArray[index] = 1.0 / unwrapped
}
}
The follow code is the API used to get the 3 digit currency codes and the exchange rates (called via UpdateRates).
class GetCurrency: Codable {
let id = UUID()
var getCurrencies: [String : [String: Double]] = [:]
required public init(from decoder: Decoder) throws {
do{
print(#function)
let baseContainer = try decoder.singleValueContainer()
let base = try baseContainer.decode([String : [String: Double]].self)
for key in base.keys{
getCurrencies[key] = base[key]
}
}catch{
print(error)
throw error
}
}
}
class CurrencyViewModel: ObservableObject{
#Published var results: GetCurrency?
#Published var selectedBaseCurrency: String = "usd"
func UpdateRates() {
let baseUrl = "https://cdn.jsdelivr.net/gh/fawazahmed0/currency-api#1/latest/currencies/"
let baseCur = selectedBaseCurrency // usd, eur, cad, etc
let requestType = ".json"
guard let url = URL(string: baseUrl + baseCur + requestType) else {
print("Invalid URL")
return
}
let request = URLRequest(url: url)
URLSession.shared.dataTask(with: request) { data, response, error in
if let data = data {
do{
let decodedResponse = try JSONDecoder().decode(GetCurrency.self, from: data)
DispatchQueue.main.async {
self.results = decodedResponse
// this prints out the complete table of currency code and exchange rates
print(self.results?.getCurrencies["usd"] ?? 0.0)
}
} catch {
//Error thrown by a try
print(error)//much more informative than error?.localizedDescription
}
}
if error != nil {
//data task error
print(error!)
}
}.resume()
}
}

Answer 1

Thanks lorem ipsum for your help. Below is the updated ASI logic that copies the exchange rates to the rateArray using key/value lookups.
class CurrencyViewModel: ObservableObject{
#Published var results: GetCurrency?
#Published var rateArray = [Double] ()
init() {
if UserDefaults.standard.array(forKey: "rates") != nil {
rateArray = UserDefaults.standard.array(forKey: "rates") as! [Double]
}else {
rateArray = [Double] (repeating: 0.0, count: 160)
UserDefaults.standard.set(self.rateArray, forKey: "rates")
}
}
func updateRates(baseCur: String) {
...
DispatchQueue.main.async {
self.results = decodedResponse
// loop through all available currencies
for index in 0..<currCode.count {
currencyCode = currCode[index]
// spacial handling for base currency
if currencyCode == baseCur {
self.rateArray[index] = 1.0000
} else {
let homeRate = self.results?.getCurrencies[baseCur]
// complement and save the exchange rate
if let unwrapped = homeRate?[currencyCode] {
self.rateArray[index] = 1.0 / unwrapped
}
}
}
}
} catch {
//Error thrown by a try
print(error)//much more informative than error?.localizedDescription
}
}
if error != nil {
//data task error
print(error!)
}
}.resume()
}
}