yeah

that was the problem it seems

is it possible to do it with KClass though?

What do you mean?

for the type param of MetadataValue

KClass requires the generic type to extend Any

ah yes, i guess it works fine

it was just the variance modifier that was causing the issue

Alright, thanks @karelpeeters !

Hey yall, isn’t it weird that

.filter

is only defined on

Map<K, V>

and not on

HashMap<K, V>

?

This leads to some chafing when filtering a

HashMap

, because a

Map

is returned from the

filter

call

Well, there is no guarantee which

Map

implementation is used by

filter

for the result. You might get a

LinkedHashMap

or something entirely different.

I was expecting

hashMapOf("cow" to "grass").filter { it.key != "horse" }

to return a

HashMap

Instead, it returns a

Map

Yeah, that could be implemented with inline function with reified type, but it’s too late to change this part of stdlib

however usually concrete type doesn’t matter

Yeah, and what’s the downside of that?

someone has to write a filter implementation on every map is a pretty significant downside no?

Hey could someone help me out understand a little issue I’ve had with Kotlin. When writing a subclasses constructor the class has to call the super classes constructor before doing anything. Why is this?

that's a java requirement

oh

is that why Java SDKs always have the builder classes or static method constructors?

that would be one benefit of those patterns i suppose. but they're probably not specifically working around that restriction

They are often working around it, a factory method can do stuff to the parameters before calling the constructor.

And IIRC that's isn't a JVM requirement, it's only like that in the Java language.

ok thanks guys

man i wish kotlin had scala-style imports.

What do you mean by that?

How do I invoke this interface member?

kotlin
val clazz = ReceiverClass()
    clazz.???  //receive is not available
}

interface Data {
    fun doStuff()
}

interface Receiver {
    fun Data.receive() //implicit Data
}

class ReceiverClass : Receiver {
    override fun Data.receive() {
        doStuff()
    }
}

My book on Reactive Programming in Kotlin https://www.packtpub.com/application-development/reactive-programming-kotlin