Using Structure before Initialization - swiftui

Question

I am having initialization trouble with an exchange rate structure. In the method getRates I have been trying to implement dictionary key / value logic to copy exchange rates into an ordered array. I am getting the error "Variable 'moneyRates' used before being initialized". I tried adding a memberwise initializer but was unsure how to initialize the rate array. I have also been wondering if I should move the instance of MoneyRates to the top of the class instead of in the getRates method.
var currCode: [String] = ["usd", "afn", "all", "dzd", "amd", "ang", "aoa", "ars", "aud", "awg", "azn",
/* b */ "bsd", "bhd", "bdt", "bbd", "byr", "bzd", "bmd", "btn", "bob", "bam", "bwp", "brl", "bnd", "bgn", "bif",
/* c */ "cad", "khr", "cve", "xcd", "kyd", "xaf", "xof", "xpf", "clf", "clp", "cnh", "cny", "cop", "kmf", "cdf", "crc", "hrk", "cup", "czk"]
struct MoneyRates {
let date: String
let base: String
let rates: [String: Double]
}
class CurrencyRates: ObservableObject {
#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: 170)
UserDefaults.standard.set(self.rateArray, forKey: "rates")
}
}
// retrieve exchange rates for all 150+ countries from internet and save to rateArray
func updateRates(baseCur: String) {
print("doing update")
let baseUrl = "https://cdn.jsdelivr.net/gh/fawazahmed0/currency-api#1/latest/currencies/"
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 result = try JSONSerialization.jsonObject(with: data) as! [String:Any]
var keys = Array(result.keys)
if let dateIndex = keys.firstIndex(of: "date"),
let date = result[keys[dateIndex]] as? String, keys.count == 2 {
keys.remove(at: dateIndex)
let base = keys.first!
print("base = \(base)")
print("date = \(date)")
let rates = MoneyRates(date: date, base: base, rates: result[base] as! [String:Double])
print(rates)
self.getRates(rates: rates, baseCur: baseCur)
}
} catch {
print(error)
}
}
}.resume()
}
// copy rates from MoneyRates to rateArray
func getRates (rates: MoneyRates, baseCur: String) -> () {
var moneyRates: MoneyRates
var currencyCode: String = ""
// loop through all available currencies
// the rates are stored in the same order as currCode
for index in 0..<currCode.count {
currencyCode = currCode[index]
// special handling for base currency
if currencyCode == baseCur {
rateArray[index] = 1.0000
} else {
print(currencyCode)
if moneyRates.rates[currencyCode] != nil { // error here
let unwrapped = (moneyRates.rates[currencyCode]!) // and here (same)
print( unwrapped)
rateArray[index] = 1.0 / unwrapped // want inverse exchange rate
}
}
UserDefaults.standard.set(self.rateArray, forKey: "rates")
}
}
}

Answer 1

The error you are getting is because you declare the variable "moneyRates"
but you do not instantiate it to something.
var moneyRates: MoneyRates
In other words there is nothing in "moneyRates",
but you are trying to get something from it in:
if moneyRates.rates[currencyCode] != nil {
...
}
So populate "moneyRates" with some data.