Decode nested JSON arrays and dictionaries in Swift using Structs with JSONserialization - ios

Question

I am trying to create some structs to decode some JSON received from an API using JSONSerialization.jsonObject(with: data, options: [])
This is what the JSON looks like:
{"books":[{"title":"The Fountainhead.","author":"Ayn Ranyd"},{"title":"Tom Sawyer","author":"Mark Twain"},{"title":"Warhol","author":"Blake Gopnik"}]}
Here are the structs that I am trying to use for decoding.
struct BooksReturned : Codable {
let books : [Book]?
}
struct Book : Codable {
let BookParts: Array<Any>?
}
struct BookParts : Codable {
let titleDict : Dictionary<String>?
let authorDict : Dictionary<String>?
}
The error is:
The given data was not valid JSON.", underlyingError: Optional(Error Domain=NSCocoaErrorDomain Code=3840 "JSON text did not start with array or object and option to allow fragments not set." UserInfo={NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.})))
The non-working code I am using to decode is:
let task = session.dataTask(with: url) { data, response, error in
if let data = data, error == nil {
let nsdata = NSData(data: data)
DispatchQueue.main.async {
if let str = String(data: data, encoding: .utf8) {
let json = try? JSONSerialization.jsonObject(with: data, options: [])
do {
let mybooks = try JSONDecoder().decode(BooksReturned.self, from: data)
//do something with book
}
} catch {
print(error.localizedDescription)
print(error)
}
}
}
} else {
// Failure
}
}
task.resume()
}
I have some very limited ability to change JSON. The only thing I can do is remove the "books" : Everything else is received from an external API.
Thanks for any suggestions on how to get this to work.

Answer 1

The JSON you provided seems to be valid. Modify your Book model and the decoding part as the following.
Model:
struct Book: Codable {
let title, author: String
}
Decoding:
let task = session.dataTask(with: url) { data, response, error in
if let data = data, error == nil {
DispatchQueue.main.async {
do {
let mybooks = try JSONDecoder().decode(BooksReturned.self, from: data)
print(mybooks)
}
} catch {
print(error.localizedDescription)
print(error)
}
}
} else {
// Failure
}
task.resume()