Kotlin - generics - Know Your Ins from Your Outs - in keyword, out keyword

Head First Kotlin
A Brain-Friendly Guide
楽天ブックス(Kobo) 紀伊國屋書店(Kinoppy)

開発環境

• macOS Mojave - Apple (OS)
• Windows 10 Pro (OS)
• IntelliJ IDEA CE(Community Edition) (IDE(統合開発環境))
• Kotlin (プログラミング言語)

Head First Kotlin: A Brain-Friendly Guide (Dawn Griffiths(著)、David Griffiths(著)、O'Reilly Media)のChapter 10(generics - Know Your Ins from Your Outs)、Sharpen your pencil(321)の解答を求めてみる。

コード

open class Food
class VeganFood : Food()
interface Seller<out T>
class FoodSeller : Seller<Food>
class VeganFoodSeller : Seller<VeganFood>
interface Consumer<in T>
class Person : Consumer<Food>
class Vegan : Consumer<VeganFood>

fun main() {
    var foodSeller: Seller<Food>
    foodSeller = FoodSeller()
    foodSeller = VeganFoodSeller()

    var veganFoodConsumer: Consumer<VeganFood>
    veganFoodConsumer = Vegan()
    veganFoodConsumer = Person()
}

入出力結果

Process finished with exit code 0