I have an interface with a function that has the signature `

Question

I have an interface with a function that has the signature `fun lt T Any gt asArray tClazz Class lt T gt Array lt T gt ` how ever I have no idea how to return an Array of type T in Kotlin on a non reified function with only the Class as argument

diesieben07 · Answer

On the JVM `val array = java lang reflect Array newInstance componentType length `

diesieben07 · Answer

~On JS you can use `val array = js unsafeCast lt Array lt T gt gt `~ only works if T is not a primitive type

Marko Mitic · Answer

` Array lt T gt ` smile

diesieben07 · Answer

That does not work if `T` is not reified

wbertan · Answer

`inline fun lt reified T Any gt asArray tClazz Class lt T gt Array lt T gt = arrayOf ` Cannot use as `inline`

mantono · Answer

Thank you < diesieben07> I thought reflection might be the solution but I could not find out how

mantono · Answer

< wbertan> No it is not possible when it is part of an interface

wbertan · Answer

Oh didn t know disappointed

Marko Mitic · Answer

Arrays are tricky

mantono · Answer

< diesieben07> I get a ClassCastExcpetion tough thinking face

diesieben07 · Answer

Show your code

mantono · Answer

`val array Array lt T gt = java lang reflect Array newInstance tClazz size as Array lt T gt `

mantono · Answer

If I do not cast it it will just be `Any` and I will be unable to use it for anything

diesieben07 · Answer

It works for me

diesieben07 · Answer

What did you use as `tClazz`

mantono · Answer

Can I see your code

mantono · Answer

Long

diesieben07 · Answer

If you use primitive types Int Short etc you need to ensure to use `Int class javaObjectType` otherwise you will get a `LongArray` not a `Array lt Long gt ` from `Array newInstance`

mantono · Answer

Aha I see

diesieben07 · Answer

You can guard against that inside your `asArray` method ``` java lang reflect Array newInstance cls kotlin javaObjectType 10 as Array lt T gt ```

diesieben07 · Answer

Is there a specific reason you must use an array and not a list Then you would not need any of this crazyness smile

mantono · Answer

Yeah that s what the interface has specified not my interface cry I usually know better than to trying to use generic arrays in Kotlin

mantono · Answer

Now it works anyway thanks a lot < diesieben07> I would not have figured out this one by myself

mantono · Answer

Now I just need to guard for this on all primtive types

mantono · Answer

I wrote an extension function for this to List This is the final result <https gist github com mantono 914d54d0c9deb01281ca0133676968a5> once again huge thanks for the help

diesieben07 · Answer

You don t need that when you can just always call javaObjectType

diesieben07 · Answer

That means you have to guard T by any though lt T Any gt

mantono · Answer

That should be acceptable

mantono · Answer

Really nice thanks smile