Ouch, seems that I can't override abstract `StringConverter<T>` with another parametric class

# getting-started

[ValV]

Ouch, seems that I can't override abstract StringConverter<T> with another parametric class

[robin]

A class defined as BooleanStringConverter : StringConverter<Boolean> should definitely be assignable to StringConverter<Boolean>. Or am I misunderstanding what you're trying to do?

[ValV]

There are two functions: fromString(String?): T and toString(T): String which I would like to override for a couple of cases

[ValV]

And do not want to create a separate class for each type

[robin]

Oh, okay, so you would want to do a typecheck on T inside the toString function?

[ValV]

Exactly

[robin]

Well you can always just check the type of the parameter that's coming in, so for example you could do it like this:

class AnyConverter : StringConverter<Any> {
    fun toString(value: Any): String {
        when (value) {
            is String -> TODO()
            is Int -> TODO()
            else -> TODO()
        }
    }
{

[ValV]

Cool

[robin]

Oh and I forgot to say that still works if the class is parameterized:

class Converter<T> : StringConverter<T> {
    fun toString(value: T): String {
        when (value) {
            is String -> TODO()
            is Int -> TODO()
            else -> TODO()
        }
    }
{

[ValV]

But for

fun fromString(value: String?): Any {
}

it seems not so simple

[robin]

That's true. To get it there without having something else to go on this is what I would do:

class Converter<T>(val clazz: KClass<T>) : StringConverter<T> {
    fun fromString(value: String): T {
        when (clazz) {
            String::class -> TODO()
            Int::class -> TODO()
            else -> TODO()
        }
    }
    companion object {
        operator inline fun <reified T> invoke() = Converter(T::class)
    }
}

[ValV]

I thought of passing any variable to the class constructor like:

class MyConverter<T>(data: T): StringConverter<T> {
}

[robin]

Yeah, see my message - I was faster 😛

[ValV]

Is it neccessary to make clazz val?

[robin]

yeah, otherwise you can't access it from within a function body. You can make it private though.

[ValV]

Thanks