由于缺少Content-Type，因此无法解码JSON

Question

My JSONDecoder().decode can't decode data to json format, because server response has Content-Type like this "* \\ *;charset=utf8".

What I have to do in this situation? Any ideas? API link

My code:

private static let livePhotoUrlString = "https://m1.kappboom.com/livewallpapers/info?o=0&v=575"

static func getLivePhotos(completionHandler: @escaping (([LivePhoto]) -> Void)) {
    guard let livePhotoUrl = URL(string: livePhotoUrlString) else { return }
    let semaphore = DispatchSemaphore(value: 0)

    URLSession.shared.dataTask(with: livePhotoUrl) { (data, response, error) in
         do {
             guard let data = data else { return }
             let livePhotos = try JSONDecoder().decode([LivePhoto].self, from: data)
             completionHandler(livePhotos)
         } catch {
             completionHandler([])
         }
         semaphore.signal()
     }.resume()
     semaphore.wait()
}

My entity (LivePhoto):

class LivePhoto: Decodable {

    init(smallUrl: String, largeUrl: String, movieUrl: String, id: Int, isLocked: Bool, promotionalUnlock: Bool) {
        self.smallUrl = smallUrl
        self.largeUrl = largeUrl
        self.movieUrl = movieUrl
        self.id = id
        self.isLocked = isLocked
        self.promotionalUnlock = promotionalUnlock
    }

    var smallUrl: String
    var largeUrl: String
    var movieUrl: String
    var id: Int
    var isLocked: Bool
    var promotionalUnlock: Bool
}

Response headers:

Correct response (another API):

Answer 1

You need to use key names as they are in json , or write an enum with the converted names , but better to use convertFromSnakeCase

  func getLivePhotos(completionHandler: @escaping (([LivePhoto]) -> Void)) {
        guard let livePhotoUrl = URL(string: livePhotoUrlString) else { return }

        URLSession.shared.dataTask(with: livePhotoUrl) { (data, response, error) in
              print(data)
            do {
                guard let data = data else { return }
                let dec = JSONDecoder()
                dec.keyDecodingStrategy = .convertFromSnakeCase
                let livePhotos = try dec.decode([LivePhoto].self, from: data)
                completionHandler(livePhotos)
            } catch {
                print(error)
                completionHandler([])
            }

            }.resume()

    }



}

---

struct LivePhoto: Codable {
    let id: Int
    let smallUrl, largeUrl: String
    let movieUrl: String
    let isLocked, promotionalUnlock: Bool

}

Also it's a best practice to always print(error) inside the catch block , so you can know the error and fix , here there is no place for semaphores , it's only the job of the completion , also you may show an activity indicator until the request finishes as a better UX

Answer 2

Are you sure that is the problem, to me it looks like you need to define coding keys for your struct

enum CodingKeys: String, CodingKey {
    case smallUrl = "small_url"
    case largeUrl = "large_url"
    case movieUrl = "movie_url"
    case isLocked = "is_locked"
    case promotionalUnlock = "promotional_unlock"
    case id
}

Answer 3

The error is not related to the content type.

Rather than ignoring the error in the catch block print it, decoding errors are very descriptive.

} catch {
    print(error)
    completionHandler([])
}

It states

keyNotFound(CodingKeys(stringValue: "smallUrl", intValue: nil), Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: \\"smallUrl\\", intValue: nil) (\\"smallUrl\\").", underlyingError: nil))

You can see immediately that the key is small_url and your struct member is smallUrl .

The easiest solution is to add the convertFromSnakeCase key decoding strategy

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
let livePhotos = try decoder.decode([LivePhoto].self, from: data)

And you don't need the init method in the class. Declare it as struct with constant members

struct LivePhoto: Decodable {
    let smallUrl, largeUrl, movieUrl: String
    let id: Int
    let isLocked: Bool
    let promotionalUnlock: Bool
}

And please delete this horrible semaphore . As you are using a completion handler anyway it's pointless.