JSON throws nil on every request - ios

Question

First time I'm trying to parse JSON data. The output comes out -
Course (success: zero, timestamp: nil, base: nil, date: nil, courses: nil)
Why is there nil everywhere?
I tried to change the value in the "Course" and "Currency" structures but did not lead to success
import UIKit
import JavaScriptCore
struct Course: Decodable {
var success: Bool?
var timestamp: Int?
var base: String?
var date: String?
var rates: Currency?
}
struct Currency: Decodable {
var USD: Float
var AUD: Double
var CAD: Double
var PLN: Double
var MXN: Double
}
class JsonViewContoller: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let urlData: String = "http://data.fixer.io/api/latest?access_key=7ac2982c82da926b787fd2f089b110e5&symbols=USD,AUD,CAD,PLN,MXN&format=1"
guard let url = URL(string: urlData) else { return }
URLSession.shared.dataTask(with: url) { (data, response, error) in
guard let data = data else { return }
guard error == nil else { return }
do {
let course = try JSONDecoder().decode(Course.self, from: data)
print(Course())
} catch let error {
print(error)
}
}.resume()
}
}

Answer 1

I have run your code you don't need to use two structures to parse the above JSON data. You can easily get Data in a single Structure. I have modified your code as follows:-
import UIKit
struct Course: Codable {
let success: Bool?
let timestamp: Int?
let base, date: String?
let rates: [String: Double]?
}
class JsonViewContoller: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
courseData()
}
fileprivate func courseData(){
let urlData: String = "http://data.fixer.io/api/latest?access_key=7ac2982c82da926b787fd2f089b110e5&symbols=USD,AUD,CAD,PLN,MXN&format=1"
guard let url = URL(string: urlData) else { return }
URLSession.shared.dataTask(with: url) { (data, response, error) in
guard let data = data else { return }
guard error == nil else { return }
do {
let course = try JSONDecoder().decode(Course.self, from: data)
print(course)
} catch let error {
print(error)
}
}.resume()
}
}