Parsing weird jsons in swift with Codable

main.swift

import Foundation

struct StringCodingKey: CodingKey {
    let stringValue: String
    
    
    init?(stringValue: String) {
        self.stringValue = stringValue
    }
    
    var intValue: Int? {
        return nil
    }
    
    init?(intValue: Int) {
        assertionFailure()
        return nil
    }
}

struct KeyedBox<T: Codable>: Codable {
    var key: String
    var value: T
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: StringCodingKey.self)
        let key = container.allKeys[0]
        
        self.key = key.stringValue
        self.value = try container.decode(T.self, forKey: key)
    }
    
    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: StringCodingKey.self)
        try container.encode(value, forKey: StringCodingKey(stringValue: key)!)
    }
}

let json = """
{
    "hello" : "world"
}
"""
let data = json.data(using: .utf8)!
let decoder = JSONDecoder()
let parsed = try! decoder.decode(KeyedBox<String>.self, from: data)
print(parsed)