使枚举(具有关联类型)可编码，成功

enum Color {
    case red(Int)
    case green(Double)
    case blue(String)
}

enum Color: Codable {
    case red(Int)
    case green(Double)
    case blue(String)

    enum CodingKeys: String, CodingKey {
        case type
        case value
    }

    enum ColorType: String, Codable {
        case red
        case green
        case blue
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)

        switch self {
        case .red(let value):
            try container.encode(ColorType.red, forKey: .type)
            try container.encode(value, forKey: .value)
        case .green(let value):
            try container.encode(ColorType.green, forKey: .type)
            try container.encode(value, forKey: .value)
        case .blue(let value):
            try container.encode(ColorType.blue, forKey: .type)
            try container.encode(value, forKey: .value)
        }
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        let type = try container.decode(ColorType.self, forKey: .type)

        switch type {
        case .red:
            let value = try container.decode(Int.self, forKey: .value)
            self = .red(value)
        case .green:
            let value = try container.decode(Double.self, forKey: .value)
            self = .green(value)
        case .blue:
            let value = try container.decode(String.self, forKey: .value)
            self = .blue(value)
        }
    }
}

let color = Color.red(255)
let encoder = JSONEncoder()
let jsonData = try encoder.encode(color)