Kotlin - Dynamically instantiate all inner classes

Here is the situation I am looking to solve - A service is consuming JSON and doing some processing. Based on a string value in one of the JSON fields I want to instantiate one of a number of classes implementing an interface.

In essence I am trying to give the JSON input the ability to control which functionality to use.

A simplified version of my current solution is as follows

interface A{
    val name: String
    fun doSomething()
}

class choseImplementation(val jsonChoice: String){
    inner class B: A{
        override val name = "B"
        override fun doSomething(){// Do B things}
    }

    inner class C: A{
        override val name = "C"
        override fun doSomething(){// Do C things}
    }

    init {
        // Instantiate B and C
        // Compare B.name and C.name with jsonChoice
        // Choose the name that matches jsonChoice and expose the instantiated class
        // The exposed class will be used in downstream processing
    }
}

choseImplementation is given a string and exposes the proper implementation to be used by the system.

Right now I am manually instantiating each class within the init function and then comparing, which means I have to change the code in two places, add the D class then incorporate it in the init function

I want to be able to add a new inner class (D implements A) and have it automatically added to the process of being instantiated and selected.

Solutions outside this template are welcome

Thanks!