Why can't we just do:

class LootBox(item: Any) {
    private var loot = item
}

Instead of

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

I think with your current example, it doesn't provide much value. If you change loot to be public, then it would

class LootBox<T>(item: T) {
    var loot: T = item
}

val lootBox = LootBox("gold”)
val loot: String = lootBox.loot

vs

val lootBox = LootBox(“gold”)
val loot: String = lootBox.loot as String

The latter is unsafe, could cause a crash if T is not a String. The whole idea is to allow LootBox to work with whatever type you want. And allowing users of LootBox to know what type it contains

@Matt Rea I'm also confused what 'in' and 'out' is... I"m stuck in this book on that also

Some good examples of the usefulness of generics are collections. List, Map, etc

@Matt Rea can you explain 'in' and 'out' in simple terms?

I can try! In means that the type T can only be used as an input in the class. Example would be as a parameter to a function Out means that the type T can only be used as an output in the class. Example is as a return type of a function This is a good overview. Might require some knowledge of Java generics to know why they did it this way https://kotlinlang.org/docs/generics.html

ok thanks

Good blog post about Kotlin generics and variance (in/out) https://proandroiddev.com/understanding-generics-and-variance-in-kotlin-714c14564c47

@gildor I understand it now, after some time 🙂