sealed class Operation <out T> {

   data class InsertOperation<out T>(var insertedData: ArrayList<T>)
}

Hi, this gives

type parameter t is declared as 'out' but occurs in 'invariant' position in type t

, can anyone tell me what is correct way of handling this type of variance checking?

An

out

parameter means you are only getting values of that type out of the class. But

ArrayList

permits writing. Use a

List<T>

, which is not modifiable

my first thought was that so i have checked using list as well, but it throws the same error unfortunately. is there anything i'm missing here?

You also have

insertedData

declared as a

var

, which means you can, again, put data in.

is the second

<out T>

really necessary?

@Massimo yes, we need it, otherwise we'll not be able use it,

data class InsertOperation<out T>(val insertedData: List<T>) :Operation<T>

it'll be something like this

@Syed Faraz thanks you're right, in your snippet is the first one to be unused