How to create an Enum class that takes multiple parameters but only uses one of them for comparison-CodePudding

I want my enum class to take two parameters but only use one of them when comparing which type to initialize. Here I want the id to be passed during initialization as well but not use it to control which type gets created.

enum class ActionEnum(val action: String, val id: String) {
    URL("URL") {
        override fun start() {
            openUrl(id)
        }
    },
    START_FRAGMENT("FRAG") {
        override fun start() {
            startFragmentWithId(id)
        }
    },
    START_POPUP("POPUP"){
        override fun start() {
            startPopUpWithMessage(id)
        }
    };

    open fun start() {
    }
}

CodePudding user response：

From your question is not really clear what you intend to do with the parameter action, but I think that what you are looking for are sealed classes.

Instead of defining an enum, you can define a sealed class like this

sealed class ActionEnum(val action: String, val id: String) {
    class URL(action: String): ActionEnum(action, "URL") {
        override fun start() {
            openUrl(id)
        }
    }
    class START_FRAGMENT(action: String): ActionEnum(action, "FRAG") {
        override fun start() {
            startFragmentWithId(id)
        }
    }
    class START_POPUP(action: String): ActionEnum(action, "POPUP") {
        override fun start() {
            startPopUpWithMessage(id)
        }
    };

    open fun start() {
    }
}

You can use that like an enum which means that e.g. you have exhaustive when without the need for an else clause:

    val a: ActionEnum = ActionEnum.URL("some action")
    when(a) {
        is ActionEnum.URL -> ...
        is ActionEnum.START_FRAGMENT -> ...
        is ActionEnum.START_POPUP -> ...
        // no more cases possible because ActionEnum is sealed
    }

But you can have different instances of each "enum" element where action can have a different value - which is not possible with real enums.