Add Enum initializers from rawValue

[angelolloqui]

In Swift, when you have an enum like:

public enum PaymentMethodType: String {
    case direct = "DIRECT",  creditCard = "CREDIT_CARD"
}

The you can instantiate the enum from a rawValue like:
let type = PaymentMethodType(rawValue: "DIRECT")

In Kotlin, the equivalent would be:

enum class PaymentMethodType constructor(var rawValue: String) {
    direct("DIRECT"),  creditCard("CREDIT_CARD");
}

But that does not provide the Swift constructor from rawValue.

An option, would be to create an additional method on the Kotlin code like:

enum class PaymentMethodType constructor(var rawValue: String) {
    direct("DIRECT"),  creditCard("CREDIT_CARD");

    companion object {
        fun from(rawValue: String): PaymentMethodType? =
                values().firstOrNull { it.rawValue == rawValue }
    }
}

But this also affects the way the caller needs to invoke the instantiation to:

val type = PaymentMethodType.from(rawValue = "DIRECT")

[angelolloqui]

For reference, there is also a EnumClass.valueOf(value: String): EnumClass method in Kotlin out of the box, but that one throws an exception if the value is not found, while the Swift version returns an optional

[angelolloqui]

Wait, we should try this approach:

enum class PaymentMethodType constructor(var rawValue: String) {
    direct("DIRECT"),  creditCard("CREDIT_CARD");

    companion object {
         operator fun invoke(rawValue: String) = PaymentMethodType.values().firstOrNull { it.rawValue == rawValue }
    }
}

Because, apparently that works as well, and allows to keep the same caller code:

val method = PaymentMethodType(rawValue = "DIRECT")

[torlangballe]

Great! Strange way that constructor is made :-)

…

On 18 Feb 2019, at 12:32, Angel G. Olloqui ***@***.***> wrote: Wait, we should try this approach: enum class PaymentMethodType constructor(var rawValue: String) { direct("DIRECT"), creditCard("CREDIT_CARD"); companion object { operator fun invoke(rawValue: String) = PaymentMethodType.values().firstOrNull { it.rawValue == rawValue } } } Because, apparently that works as well, and allows to keep the same caller code: val method = PaymentMethodType(rawValue = "DIRECT") — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#94 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AB-irqr8oc8puseI2co4I5oYAW25TtaIks5vOo8ygaJpZM4bAoMm>.

[torlangballe]

Do you want me to add this in a new branch, or will you do it?

[angelolloqui]

I think you already got some stuff working for this, didn't you? if so, please go ahead. Otherwise, I will try to find some time, but as usual, I can not promise on dates.

[angelolloqui]

Merged with #97