IOS/Swift: Parse JSON data and dictionary - ios

Question

I am trying to parse some nested JSON retrieved through an API but am having trouble isolating specific key-value pairs. In fact, I have some confusion over the difference between the JSON data and the dictionary obtained through serialization.
To retrieve the data I am using:
let task = URLSession.shared.dataTask(with: request) { data, response, error in
guard let data = data, error == nil else {
return
}
To convert the data to a JSON dictionary, I am doing
do {
let stringDic = try JSONSerialization.jsonObject(with: data, options: []) as? [String : Any]
} catch let error {
print(error)
}
When printed, this produces nested output of the form:
Optional(["document_tone": {
"tone_categories" = (
{
"category_id" = "emotion_tone";
"category_name" = "Emotion Tone";
and so forth
My question is how can I get a unique value such as that for the key category_name?
If I try to use
let myCat = stringDic["category_name"]
Fix-it requires let document_tone = stringDic?["document_tone"] which if printed to console just prints whole dictionary over again.
Thanks in advance for any suggestions.

Answer 1

It's pretty easy: () is array, {} is dictionary and the compiler must know the static types of all subscripted objects:
if let documentTone = stringDic?["document_tone"] as? [String:Any],
let toneCategories = documentTone["tone_categories"] as? [[String:Any]] {
for category in toneCategories {
print(category["category_name"])
}
}

Answer 2

I think it's better to use Decodable
struct Root:Decodable {
let documentTone : InnerItem
}
struct InnerItem:Decodable {
let toneCategories: [BottomItem]
}
struct BottomItem:Decodable {
let categoryId: String
let categoryName: String
}
do {
let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
let result = try decoder.decode(Root.self, from: data)
//print all names
result.documentTone.toneCategories.forEach {print($0.categoryName) }
} catch {
print(error)
}