parameter-extended-json.swift

import Foundation

struct C : Codable {
    var name: String
    var age: Int
}

struct D : Codable {
    var power: Float
    var size: Float
}

// 一つの手

struct C2A : Decodable {
    var c: C
    var d: D
    
    init(from decoder: Decoder) throws {
        self.c = try C(from: decoder)
        self.d = try D(from: decoder)
    }
}

// 更にもう一手
struct C2B : Decodable {
    var name: String
    var age: Int
    var power: Float
    var size: Float
    
    init(from decoder: Decoder) throws {
        let c2 = try C2A(from: decoder)
        
        self.name = c2.c.name
        self.age = c2.c.age
        self.power = c2.d.power
        self.size = c2.d.size
    }
}

let json = """
{
"name": "aa",
"age": 3,
"power": 0,
"size": 1
}
"""

let decoder = JSONDecoder()
let x = try decoder.decode(C2B.self, from: json.data(using: .utf8)!)
dump(x)

/*
 ▿ CommandLineSandbox.C2B
 - name: "aa"
 - age: 3
 - power: 0.0
 - size: 1.0
 */