CODEWITHSUNDEEP
constructorkotlininner-classes
Pravin Sonawane
Pravin Sonawane

Reputation: 1833

Kotlin: Constructor of inner class can be called only with receiver of containing class

I was trying inner classes in Kotlin and came across this error but didn't quite understand it. I tried to look at the documentation here but didn't quite get any direction as to how outer classes can access inner class constructors

class OuterClass {

  fun someFun(): InnerClassSuper {
    return InnerClassX("Hello") //Error: Constructor of inner class InnerClassX can be called only with receiver of containing class
  }

  sealed class InnerClassSuper {

    inner class InnerClassX(val x: String): InnerClassSuper()

  }
}

Would appreciate if someone explains the error and directs how to fix it. Thanks.

Upvotes: 26

Views: 18059

Answers (3)

javaxian
javaxian

Reputation: 2394

The easiest way would be to place the definition of your InnerClassX outside of the sealed InnerClassSuper, then the InnerClassX will become an inner class of OuterClass and will be able to be instantiated and to reference its members:

class OuterClass {

  fun someFun(): InnerClassSuper {
    return InnerClassX("Hello") // this is legit now
  }

  sealed class InnerClassSuper

  inner class InnerClassX(val x: String): InnerClassSuper()

}

Upvotes: 1

shivambhanvadia
shivambhanvadia

Reputation: 527

We can use it this way too

OuterClassName().NestedClassName()

Upvotes: 26

hotkey
hotkey

Reputation: 148089

Your code basically means that InnerClassX is an inner class of InnerClassSuper, not OuterClass, so the error means you need to provide a receiver object of InnerClasssSuper upon construction of InnerClassX.

At this point, Kotlin allows having neither an inner sealed class nor a derived class for a sealed class as an inner class of another class.

You can, however, make an abstract class derived from the sealed one and inherit from it inside the OuterClass:

sealed class SealedClassSuper {
    abstract class SealedClassChild(val x: String): SealedClassSuper()
}

class OuterClass {
    inner class InnerClassX(x: String) : SealedClassSuper.SealedClassChild(x)

    fun someFun(): SealedClassSuper {
        return InnerClassX("Hello")
    }
}

Upvotes: 10

Related Questions