Kotlin abstract class with generic param and methods which use type param

Question

I\'m trying to create an abstract class with generic parameter which will have subclasses which should call methods without having to specify type parameters

Answer 1

You can give the abstract class a casting lambda:

abstract class AbstractClass(val delegate: MyService, val castFn: (Any) -> T) {
    fun myMethod(param: Any): T? {
        return castFn(delegate.myMethod(param))
    }
}

class TesterWork(delegate: MyService) : AbstractClass(delegate, {it as Tester}) {

}

You could maybe also make the class non-abstract, give it an interface and let an inline function create it:

interface Inter {
    fun myMethod(param: Any): T
}

class NotAbstractClass(val delegate: MyService, val castFn: (Any) -> T) : Inter {
    override fun myMethod(param: Any): T {
        return castFn(delegate.myMethod(param))
    }
}

inline fun  makeClass(delegate: MyService): Inter {
    return NotAbstractClass(delegate, { it as T })
}

Then you can delegate like this:

class TesterWork(delegate: MyService) : Inter by makeClass(delegate)

val service: MyService = MyService()
val t: Tester? = TesterWork(service).myMethod("test")