Kotlin Programming: The Big Nerd Ranch Guide, First Edition

Generic Functions

Generic type parameters also work with functions. That is good news, since there is currently no way for a player to retrieve loot from a loot box.

Time to fix that. Add a function that lets a player fetch the item if and only if the box is open. Track whether the box is open by adding an open property.

Listing 17.3  Adding a fetch function (Generics.kt)

class LootBox<T>(item: T) {
    var open = false
    private var loot: T = item

    fun fetch(): T? {
       return loot.takeIf { open }
    }
}

Here you define a generic function, fetch, that returns T – the generic type parameter specified on the LootBox class, which is a placeholder for the type of item.

Note that if fetch were defined outside of LootBox, type T would not ...