Kotlin中的密封类和密封接口及其应用场景

sealed class Result<out T> {
    data class Success<T>(val data: T) : Result<T>()
    data class Error(val error: Exception) : Result<Nothing>()
}

sealed class Animal
class Dog(val name: String): Animal()
class Cat(val name: String): Animal()
fun makeSound(animal: Animal) = when (animal) {
    is Dog -> println("${animal.name} says woof!")
    is Cat -> println("${animal.name} says meow!")
}
val myDog = Dog("Rufus")
val myCat = Cat("Whiskers")
makeSound(myDog) // outputs: "Rufus says woof!"
makeSound(myCat) // outputs: "Whiskers says meow!"

sealed interface State {
    object Idle : State
    data class Loading(val message: String) : State
    data class Error(val error: Throwable) : State
    data class Success(val data: Any) : State
}

sealed interface Animal {
    val name: String
    fun makeSound()
}
class Dog(override val name: String): Animal {
    override fun makeSound() {
        println("$name says woof!")
    }
}
class Cat(override val name: String): Animal {
    override fun makeSound() {
        println("$name says meow!")
    }
}
val myDog = Dog("Rufus")
val myCat = Cat("Whiskers")
myDog.makeSound() // outputs: "Rufus says woof!"
myCat.makeSound() // outputs: "Whiskers says meow!"