Swift 4 Not decoding JSON optional properly - json

Question

Swift noob here.
I'm trying to follow the App Development With Swift book and am running into trouble with decoding JSON data from the NASA API as given in the examples. Here's the code I'm trying to use:
struct PhotoInfo: Codable {
var title: String
var description: String
var url: URL
var copyright: String?
enum CodingKeys: String, CodingKey {
case title
case description = "explanation"
case url
case copyright
}
init(from decoder: Decoder) throws {
let valueContainer = try decoder.container(keyedBy: CodingKeys.self)
self.title = try valueContainer.decode(String.self, forKey: CodingKeys.title)
self.description = try valueContainer.decode(String.self, forKey: CodingKeys.description)
self.url = try valueContainer.decode(URL.self, forKey: CodingKeys.url)
self.copyright = try valueContainer.decode(String.self, forKey: CodingKeys.copyright)
}
}
func fetchPhotoInfo(completion: #escaping (PhotoInfo?) -> Void) {
let baseURL = URL(string: "https:/
let query: [String: String] = [
"api_key": "yN3**0scRWo12gCa25TWBcfp3rcuAnoeqwbpvLPn",
"date": "2011-07-13"
]
let url = baseURL.withQueries(query)!
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
let jsonDecoder = JSONDecoder()
if let data = data,
let photoInfo = try? jsonDecoder.decode(PhotoInfo.self, from: data) {
print(data)
completion(photoInfo)
} else {
print("Either no data was returned, or data was not properly decoded.")
completion(nil)
}
}
task.resume()
}
When I remove the copyright code from the PhotoInfo struct, it decodes the JSON and prints the data (line 36). Otherwise, it doesn't deserialize it. Is there a way I can troubleshoot why this is happening? Does it have something to do with the optional?

Answer 1

If copyright is optional , then you can make use of decodeIfPresent.
self.copyright = try valueContainer.decodeIfPresent(String.self, forKey: CodingKeys.copyright)

Answer 2

EDIT: Updated per #matt's comments.
technerd's answer is probably best, but I faced the same problem and dealt with it by changing try to try?. That's how it was presented in previous exercises, anyway. However, as #matt points out, this doesn't deal with the possibility that the copyright information isn't simply missing, but in fact something other than what was expected. Using try? in tandem with an if let statement provides at least basic feedback.