Refactoring Kotlin method using a lambda

Question

I have the following emun class to represent my navigation bar views.

enum class NavigationPosition(val position: Int, val id: Int) {
    HOME(0, R.id.nav_home),
    SEARCH(1, R.id.nav_search),
    PROFILE(2, R.id.nav_profile),
    SETTINGS(3, R.id.nav_settings);
}

I'm currently using the following method to do a reverse lookup by position

fun getByPosition(position: Int): NavigationPosition = when (position) {
    0 -> NavigationPosition.HOME
    1 -> NavigationPosition.SEARCH
    2 -> NavigationPosition.PROFILE
    3 -> NavigationPosition.SETTINGS
    else ->  NavigationPosition.HOME
}

var navigationPosition = getByPosition(position)

Is there a simpler way I can refactor getByPosition by using a Kotlin lambda or extension function?

Answer 1

As already mentioned, you can use NavigationPosition.values(). However, the current ways proposed are NOT memory efficient. The values function creates a new array every time it is called. I highly recommend you cache it in a static variable to make sure it's not initialized every time you call it, as this isn't efficient.

Combining a comparative approach with a cached approach, you can use a companion object inside the enum. Now, like I said, caching the values is the best option here, so in addition to a method (as mentioned in both the other answers), you also create a field containing the values, to avoid re-calling it every time you call the method.

companion object {
    private val values = values()
    fun getPositionById(id: Int) = if(id < values.size && id >= 0) values[i] else HOME
}

Answer 2

I think you want this:

NavigationPosition.values()[position]

NavigationPosition.values() is an array containing the enum values.

So you can get the same result by:

fun getByPosition(position: Int): NavigationPosition  {
    return if (position >= NavigationPosition.values().size)
        NavigationPosition.HOME
    else
        NavigationPosition.values()[position]
}