using decodable to capture array of nested objects in single line - ios

Question

Below is my json response and the struct which I need to costruct out of it.
condition: I would not like to create any other struct apart from Response,Media and would like to parse in single line as specified below.
{
"name": "xxxx",
"title": "xxxxxxx",
"assets": [
{
"items": [
{
"id": "eeee",
"desc": "rrrrrr"
}, {
"id": "eeee",
}, {
"desc": "rrrrrr"
}]
}]
}
struct Response {
let name : String
let title : string
let items : [Media]
private enum codingKeys : String, CodingKey {
case name = "name"
case title = "title"
case items = "assets.items"
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: codingKeys.self)
name = try container.decode(String.self, forKey: .name)
title = try container.decode(TrayLayout.self, forKey: .title)
items = try container.decode([Media].self, forKey: .items)
}
}

Answer 1

I managed to find a solution for your problem.
Considering following is sample json
let jsonString = """
{
"name": "xxxx",
"title": "xxxxxxx",
"assets": [
{
"items": [
{
"id": "id11",
"desc": "desc11"
}, {
"id": "id12",
}, {
"desc": "desc13"
}]
},{
"items": [
{
"id": "id21",
"desc": "desc21"
}, {
"id": "id22",
}, {
"desc": "desc23"
}]
}]
}
"""
Your structures will look as below
struct Media: Codable {
let id,desc: String?
enum CodingKeys: String, CodingKey {
case id,desc
}
}
struct Response: Decodable {
let name,title: String?
let items: [Media]?
enum CodingKeys: String, CodingKey {
case name,title,items
case assets = "assets"
}
// Decoding
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
name = try container.decode(String.self, forKey: .name)
title = try container.decode(String.self, forKey: .title)
// Here as the assets contains array of object which has a key as items and then again consist of a array of Media we need to decode as below
let assets = try container.decode([[String:[Media]]].self, forKey: .assets)
// At this stage will get assets with a array of array so we first map and retrive the items and then reduce them to one single array
items = assets.compactMap{$0[CodingKeys.items.rawValue]}.reduce([], +)
}
}
At the end it's time to use it as follows
let data = jsonString.data(using: .utf8)!
let myResponse = try! JSONDecoder().decode(Response.self, from: data)
Now you can access the data as below
myResponse.name
myResponse.title
myResponse.items
Hope this basic code helps you to achieve what you want to do. And then you can go ahead and do more nested parsing(s).
I would like to thanks Nic Laughter for such a detailed article; by referring which I managed to come with above solution.

Answer 2

Found a new way:
struct Media: Codable {
let id,desc: String?
enum CodingKeys: String, CodingKey {
case id,desc
}
}
struct Response: Decodable, CustomStringConvertible {
let name,title: String?
#NestedKey
let items: [Media]?
enum CodingKeys: String,NestableCodingKey {
case name,title,
case items = "assets/items"
}
}

Answer 3

You can try this:
struct Response: Decodable {
let name, title: String
let assets: [Assets]
}
struct Assets: Decodable {
let items: [Items]
}
struct Items: Decodable {
let id, desc: String
}
Then you can just decode it like this:
guard let response = try? JSONDecoder().decode(Response.self, from: data) else { print("Response not parsed"); return }