@KilometersPerHour

對於 Swift 沒有自動支援 Encode/Decode 的型別，我們可以利用 Property Wrapper 來讓自訂型別自動做編碼解碼的動作。

@KilometersPerHour

@propertyWrapper
struct KilometersPerHour {
    var wrappedValue: Measurement<UnitSpeed>
}

extension KilometersPerHour: Codable {
    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        let rawValue = try container.decode(Double.self)

        wrappedValue = Measurement(
            value: rawValue,
            unit: .kilometersPerHour
        )
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        try container.encode(wrappedValue.value)
    }
}

📘 參考

• Formatting numbers in Swift - Sundell
• How to convert units using Unit and Measurement - Hacking with Swift

🍎 官方

• Foundation > Units and Measurement

  • Measurement

👥 相關

• 📦 Measurement