Why am I getting an error when parsing response in swift

Question

I am trying to call an API and I am trying to map the response to a model class. But each time, I am getting a an error that invalid data.

Api call is as follows.

 let endpoint = "http://apilayer.net/api/live?access_key=baab1114aeac6b4be74138cc3e6abe79&currencies=EUR,GBP,CAD,PLN,INR&source=USD&format=1"
        guard let url = URL(string: endpoint) else {
            completed(.failure(.invalidEndPoint))
            return
        }
        let task = URLSession.shared.dataTask(with: url) { data, response, error in
            
            if let _ = error {
                completed(.failure(.unableToComplete))
                return
            }
            guard let response = response as? HTTPURLResponse, response.statusCode == 200 else {
                completed(.failure(.invalidResponse))
                return
            }
            guard let data = data else {
                completed(.failure(.invalidData))
                return
            }
            do {
                let decoder = JSONDecoder()
                decoder.keyDecodingStrategy = .convertFromSnakeCase
                let convertedValues = try decoder.decode([Converted].self, from: data)
                completed(.success(convertedValues))
            } catch {
                completed(.failure(.invalidData))
            }
        }
        
        task.resume()
    }

Sample Response is as follows.

{
  "success":true,
  "terms":"https:\/\/currencylayer.com\/terms",
  "privacy":"https:\/\/currencylayer.com\/privacy",
  "timestamp":1610986207,
  "source":"USD",
  "quotes":{
    "USDEUR":0.828185,
    "USDGBP":0.736595,
    "USDCAD":1.276345,
    "USDPLN":3.75205
  }
}

Model class

struct Converted: Codable {
    
        let success: Bool
       let terms, privacy: String?
       let timestamp: Int?
       let source: String?
       let quotes: [String: Double]?
}

Can someone help me to understand where I am getting wrong?. Thanks in advance.

Answer 1

Error messages can sometimes help. If you catch the error and print it, it reads:

typeMismatch(Swift.Array, Swift.DecodingError.Context(codingPath: [], debugDescription: "Expected to decode Array but found a dictionary instead.", underlyingError: nil))

So an array of Converted was expected when in fact a single object was returned. The solution is to update the expectation to match the actual response:

let convertedValues = try decoder.decode(Converted.self, from: data)