Decode JSON in Swift with changing Key at beginning - json

Question

I'm currently learning Swift and I wanted to create a little App, that gets Data about an Book via ISBN from the Openlibrary API.
Heres a Query that I use, to get Data:
https://openlibrary.org/api/books?bibkeys=ISBN:9783791504650&format=json&jscmd=data
Now the returning JSON looks like this:
{"ISBN:9783791504650": {"publishers": [{"name": "Dressler"}], "identifiers": {"isbn_13": ["9783791504650"], "openlibrary": ["OL8935767M"], "isbn_10": ["3791504657"], "librarything": ["1653"], "goodreads": ["292110"]}, "weight": "1.8 pounds", "title": "Tintenherz", "url": "https://openlibrary.org/books/OL8935767M/Tintenherz", "number_of_pages": 573, "cover": {"small": "https://covers.openlibrary.org/b/id/1027329-S.jpg", "large": "https://covers.openlibrary.org/b/id/1027329-L.jpg", "medium": "https://covers.openlibrary.org/b/id/1027329-M.jpg"}, "subject_places": [{"url": "https://openlibrary.org/subjects/place:italy", "name": "Italy"}], "subjects": [{"url": "https://openlibrary.org/subjects/fathers_and_daughters", "name": "Fathers and daughters"}, {"url": "https://openlibrary.org/subjects/characters_in_literature", "name": "Characters in literature"}, {"url": "https://openlibrary.org/subjects/magic", "name": "Magic"}, {"url": "https://openlibrary.org/subjects/storytelling", "name": "Storytelling"}, {"url": "https://openlibrary.org/subjects/fantasy", "name": "Fantasy"}, {"url": "https://openlibrary.org/subjects/bookbinding", "name": "Bookbinding"}, {"url": "https://openlibrary.org/subjects/fiction", "name": "Fiction"}, {"url": "https://openlibrary.org/subjects/books_and_reading", "name": "Books and reading"}, {"url": "https://openlibrary.org/subjects/bookbinders", "name": "Bookbinders"}, {"url": "https://openlibrary.org/subjects/authorship", "name": "Authorship"}, {"url": "https://openlibrary.org/subjects/characters_and_characteristics_in_literature", "name": "Characters and characteristics in literature"}, {"url": "https://openlibrary.org/subjects/juvenile_fiction", "name": "Juvenile fiction"}, {"url": "https://openlibrary.org/subjects/kidnapping", "name": "Kidnapping"}], "subject_people": [{"url": "https://openlibrary.org/subjects/person:meggie", "name": "Meggie"}, {"url": "https://openlibrary.org/subjects/person:mo", "name": "Mo"}, {"url": "https://openlibrary.org/subjects/person:dustfinger", "name": "Dustfinger"}, {"url": "https://openlibrary.org/subjects/person:capricorn", "name": "Capricorn"}, {"url": "https://openlibrary.org/subjects/person:basta", "name": "Basta"}, {"url": "https://openlibrary.org/subjects/person:mortola", "name": "Mortola"}, {"url": "https://openlibrary.org/subjects/person:fenoglio", "name": "Fenoglio"}, {"url": "https://openlibrary.org/subjects/person:elinor", "name": "Elinor"}, {"url": "https://openlibrary.org/subjects/person:resa", "name": "Resa"}, {"url": "https://openlibrary.org/subjects/person:the_shadow", "name": "The Shadow"}], "key": "/books/OL8935767M", "authors": [{"url": "https://openlibrary.org/authors/OL2704045A/Cornelia_Funke", "name": "Cornelia Funke"}], "publish_date": "2003", "ebooks": [{"formats": {}, "preview_url": "https://archive.org/details/tintenherz00funk", "availability": "restricted"}]}}
As you can see, the JSON starts with a Key, that includes the ISBN Number of given Book.
Currently, I have a File "Books.swift", which looks like this:
struct Books: Codable {
let isbn: Isbn?
enum CodingKeys: String, CodingKey {
case isbn
}
}
struct Isbn: Codable {
let publishers: [Publisher]?
let identifiers: Identifiers?
let weight: String?
let title: String?
let url: String?
let numberOfPages: Int?
let cover: Cover?
let subjectPlaces: [Author]?
let subjects: [Author]?
let subjectPeople: [Author]?
let key: String?
let authors: [Author]?
let publishDate: String?
let ebooks: [Ebook]?
enum CodingKeys: String, CodingKey {
case publishers = "publishers"
case identifiers = "identifiers"
case weight = "weight"
case title = "title"
case url = "url"
case numberOfPages = "number_of_pages"
case cover = "cover"
case subjectPlaces = "subject_places"
case subjects = "subjects"
case subjectPeople = "subject_people"
case key = "key"
case authors = "authors"
case publishDate = "publish_date"
case ebooks = "ebooks"
}
}
// MARK: - Author
struct Author: Codable {
let url: String?
let name: String?
enum CodingKeys: String, CodingKey {
case url = "url"
case name = "name"
}
}
// MARK: - Cover
struct Cover: Codable {
let small: String?
let large: String?
let medium: String?
enum CodingKeys: String, CodingKey {
case small = "small"
case large = "large"
case medium = "medium"
}
}
// MARK: - Ebook
struct Ebook: Codable {
let formats: Formats?
let previewURL: String?
let availability: String?
enum CodingKeys: String, CodingKey {
case formats = "formats"
case previewURL = "preview_url"
case availability = "availability"
}
}
// MARK: - Formats
struct Formats: Codable {
}
// MARK: - Identifiers
struct Identifiers: Codable {
let isbn13: [String]?
let openlibrary: [String]?
let isbn10: [String]?
let librarything: [String]?
let goodreads: [String]?
enum CodingKeys: String, CodingKey {
case isbn13 = "isbn_13"
case openlibrary = "openlibrary"
case isbn10 = "isbn_10"
case librarything = "librarything"
case goodreads = "goodreads"
}
}
// MARK: - Publisher
struct Publisher: Codable {
let name: String?
enum CodingKeys: String, CodingKey {
case name = "name"
}
}
I used an Online Converter for this, but it also included the ISBN for the book I used to get sample data.
And heres where the Request is started:
#IBAction func sendISBNSearchRequest(_ sender: Any) {
bookDataArray = [] //Empty Array, so there is no interfering old Data
let isbnUserInput: String = isbnInputfield.text! //Read UserInput from Textinputfield and save it into a String
self.loadingIndicator.startAnimating()
if (isbnUserInput.isNumeric && (isbnUserInput.count == 10 || isbnUserInput.count == 13)){
// Checks if user input only contains numbers as ISBN-Numbers only consists of numbers, not characters
// Also Check if it is a valid ISBN Number with 10 or 13 Numbers
let searchURL = "https://openlibrary.org/api/books?bibkeys=ISBN:\(isbnUserInput)&format=json&jscmd=data"
guard let url = URL(string: searchURL) else {
print("Error: cannot create URL")
return
}
let urlRequest = URLRequest(url: url)
let session = URLSession.shared
let task = session.dataTask(with: urlRequest) { data, response, error in
guard let data = data else {
return
}
let response = response as? HTTPURLResponse
if (response?.statusCode==200){
do{
let object = try JSONDecoder().decode(Books.self, from: data)
print(object)
DispatchQueue.main.async {
self.loadingIndicator.stopAnimating()
}
return
}catch{
print(error)
}
}
else{
self.loadingIndicator.stopAnimating()
}
}
task.resume()
}
else{
self.loadingIndicator.stopAnimating()
}
}
Is there any way to make it work for every request / ISBN-Number?
I'm still learning and the only way I see at the moment would be to create a case for every existing ISBN Number... :(

Answer 1

Alternatively write a custom initializer to separate the ISBN number
struct Books: Decodable {
let isbn: String
let book : Isbn
init(from decoder : Decoder) throws {
let container = try decoder.singleValueContainer()
let data = try container.decode([String:Book].self)
let key = data.keys.first!
isbn = key.components(separatedBy: ":").last!
book = data[key]!
}
}
do {
let object = try JSONDecoder().decode(Books.self, from: data)
print(object.isbn)
...
And you can get rid of the CodingKeys by adding the .convertFromSnakeCase key decoding strategy and making the names of the struct members conform to the conversion rules.
And it's bad practice to declare everything carelessly as optional.
PS:
Hey openlibrary.org, why not more appropriate
{"ISBN":"9783791504650","item":{"publishers":...

Answer 2

Use dictionary type [String: Isbn] instead of object of type Books:
let dictionary = try JSONDecoder().decode([String:Isbn].self, from: data)
print(dictionary["ISBN:\(isbnNumber)"])