extension function in a kotlin using super

Question

How to call extension function of the base class in a derived class using the super keyword?

I tried to call using super but it doesn't work.

 open class abc {
     open fun aa() {
         println("function in abc")
     }
 }
 fun abc.sum() {
     println("extension function")
 }
 class ab: abc() {

     override fun aa() {
         super.aa()
         println("functon in ab")
     }
     fun sum() {
         super.sum()
         println("sum function")
     }
 }
 fun main(args: Array < String > ) {
     var aa: ab = ab()
     aa.aa()
     aa.aa()
     aa.sum()
 }

Here is the 16th number line error comes, I can't call the extension function.

Answer 1

As you created the extension out of the class it is no more member of that class. You are able to call super.aa() as it is the member of the abc class.

In order to use that method you have to call it in following way.

open class abc {
    open fun aa() {
        println("function in abc")
    }
}
fun abc.sum() {
    println("extension function")
}
class ab: abc() {

    override fun aa() {
        super.aa()
        println("functon in ab")
    }
    fun sum() {
        (this as abc).sum()
        println("sum function")
    }
}
fun main(args: Array < String > ) {
    var aa: ab = ab()
    aa.aa()
    aa.aa()
    aa.sum()
}

For more info refer this link