Swift Codable: Use a parent's key as as value - swift

Question

I have a JSON that has ID's in the root level:
{
"12345": {
"name": "Pim"
},
"54321": {
"name": "Dorien"
}
}
My goal is to use Codable to create an array of User objects that have both name and ID properties.
struct User: Codable {
let id: String
let name: String
}
I know how to use Codable with a single root level key and I know how to work with unknown keys. But what I'm trying to do here is a combination of both and I have no idea what to do next.
Here's what I got so far: (You can paste this in a Playground)
import UIKit
var json = """
{
"12345": {
"name": "Pim"
},
"54321": {
"name": "Dorien"
}
}
"""
let data = Data(json.utf8)
struct User: Codable {
let name: String
}
let decoder = JSONDecoder()
do {
let decoded = try decoder.decode([String: User].self, from: data)
decoded.forEach { print($0.key, $0.value) }
// 54321 User(name: "Dorien")
// 12345 User(name: "Pim")
} catch {
print("Failed to decode JSON")
}
This is what I'd like to do:
let decoder = JSONDecoder()
do {
let decoded = try decoder.decode([User].self, from: data)
decoded.forEach { print($0) }
// User(id: "54321", name: "Dorien")
// User(id: "12345", name: "Pim")
} catch {
print("Failed to decode JSON")
}
Any help is greatly appreciated.

Answer 1

You can use a custom coding key and setup User as below to parse unknown keys,
struct CustomCodingKey: CodingKey {
let intValue: Int?
let stringValue: String
init?(stringValue: String) {
self.intValue = Int(stringValue)
self.stringValue = stringValue
}
init?(intValue: Int) {
self.intValue = intValue
self.stringValue = "\(intValue)"
}
}
struct UserInfo: Codable {
let name: String
}
struct User: Codable {
var id: String = ""
var info: UserInfo?
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CustomCodingKey.self)
if let key = container.allKeys.first {
self.id = key.stringValue
self.info = try container.decode(UserInfo.self, forKey: key)
}
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CustomCodingKey.self)
if let key = CustomCodingKey(stringValue: self.id) {
try container.encode(self.info, forKey: key)
}
}
}
let decoder = JSONDecoder()
do {
let decoded = try decoder.decode(User.self, from: data)
print(decoded.id) // 12345
print(decoded.info!.name) // Pim
} catch {
print("Failed to decode JSON")
}