is there any way to create an empty array of a generic type

Question

Andreas Sinz · Answer

Generic type unknown at compile time

Shawn · Answer

you may have to reify your generic type and inline the function in question

Shawn · Answer

``` inline fun lt reified T gt emptyGenericArray Array lt T gt return arrayOf ```

bloder · Answer

maybe this ``` inline fun lt reified T gt genericArrayOf Array lt T gt = arrayOf ```

bloder · Answer

oh sorry LOL

tschuchort · Answer

not possible The method is a class method so it can not be reified Basically I have to implement an interface of the sort `fun lt A Something gt foo bar Class lt A gt Array lt A gt `

Allan Wang · Answer

If the empty array is an immutable placeholder you can look at the empty array implementation in kotlin <https github com JetBrains kotlin blob 1 2 60 core builtins src kotlin ArrayIntrinsics kt L24> You can sort of cast an empty array for any type

kristofdho · Answer

that s what i said amp deleted since the exact same problem occurs at the `arrayOfNulls lt T gt 0 ` call `T` is again not reified

tschuchort · Answer

It s probably not supposed to be immutable The caller of this method is free to modify the returned array it will have no effect on the arrays returned to other callers Tbh I have no idea how anyone is supposed to implement this

tschuchort · Answer

god I hate the JVM

kristofdho · Answer

if it s empty there is nothing to modify it ll always be immutable

tschuchort · Answer

there s `fun lt T gt Array lt T gt plus element T Array lt T gt ` though and if I return an `arrayOfNulls lt Any gt 0 as Array lt T gt ` than calling that method on it will fail

kristofdho · Answer

the `plus` function already contains the type in `this` being an `Array lt T gt ` if you re confused as to why it s not reified

tschuchort · Answer

I m just saying there is no way I can create an empty `Array lt T gt ` for any T

tschuchort · Answer

even `arrayOfNulls lt Any gt 0 as Array lt SomeClass gt ` already doesn t work confused

kristofdho · Answer

i m trying but i cant even find something hacky deeper issue is the bad method signature because like you say you can t just magically pull a typed array out of your ass

bloder · Answer

Well it would be good if you could use list instead of array ``` fun lt T Any gt genericListOf List lt T gt = arrayOf lt KClass lt T gt gt mapNotNull it objectInstance ``` Do you know any solution like that to arrays

kristofdho · Answer

i do not recomend using it but i found this ```override fun lt T Something gt foo bar Class lt T gt Array lt T gt = java lang reflect Array newInstance bar 0 as Array lt T gt ```

diesieben07 · Answer

`java lang reflect Array newInstance` is the way to go if you need this It s ugly but perfectly fine to use

tschuchort · Answer

Thx that looks like it might work The method probably isn t gonna be called often so reflection shouldn t be a problem

diesieben07 · Answer

It s a JVM intrinsic it s not much slower than just creating a new array the normal way