CODEWITHSUNDEEP
classobjectkotlincasting
MDT
MDT

Reputation: 1695

Cast Anonymous (Any) object to class object in kotlin

Kotlin compiler is giving me error while running below :

fun main() {
    val x = object {
        val i = 1
        val k = "s"
    }
    val y = x as Planet
    if (y is Planet) {
        println("Hello " + x.i)
    }
}


data class Planet(
        var i : Int,
        var k : String
)

Error :

Exception in thread "main" java.lang.ClassCastException: FileKt$main$x$1 cannot be cast to Planet at FileKt.main (File.kt:7)
at FileKt.main (File.kt:-1) at sun.reflect.NativeMethodAccessorImpl.invoke0 (NativeMethodAccessorImpl.java:-2)

I am unable to understand why i am not able to cast Any object type to specific class object. Isn't all Kotlin classes inherit from Any super class?

please let me know what i am doing wrong here.

Upvotes: 10

Views: 28852

Answers (1)

ChristianB
ChristianB

Reputation: 2680

Kotlin is a strongly statically typed language. Every variable and every expression has a type that is known at compile time.

In your example you are not specifying the type, but that does not mean it is unknown at compile time. Kotlin uses type inference to determine its type. In your case Any.

val x: Any = object {
    // ...
}

Any is the root of the Kotlin class hierarchy. Every Kotlin class has Any as a superclass. This is the reason why you can not cast Any to Planet at runtime.

What you could do is using Kotlin safe-cast as? which returns null instead of an exception:

val planet: Planet? = x as? Planet

What you also can do, if you ever casted a Planet to Any, you can cast it back to Planet.

data class Planet(val name: String)
    
val pluto: Planet = Planet("Pluto")
val anyPlanet: Any = pluto
val planet: Planet = anyPlanet as Pluto

Upvotes: 13

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