さらに削ってみた #CodePiece

CodePiece.swift

import Foundation

struct User: Codable {
    struct Address: Codable {
        let street: String
        let city: String
        let state: String
    }
    let name: String
    let address: Address
    let url: URL?

    private enum UserCodingKeys: String, CodingKey {
        case name
        case url
    }

    public init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: UserCodingKeys.self)
        name = try container.decode(String.self, forKey: .name)
        address = try Address(from: decoder)
        url = try container.decode(URL.self, forKey: .url)
    }
}

let data = """
    {
        "name": "rizumita",
        "street": "1-2-3 Foo",
        "city": "Bar",
        "state": "Baz",
        "url": "http://yahoo.com"
}
""".data(using: .utf8)!

let decoder: JSONDecoder = JSONDecoder()
do {
    let user: User = try decoder.decode(User.self, from: data)
    print(user)
} catch {
    print(error)
}