hi, how to create an empty generic array in Kotlin...

# announcements

[Erfan]

hi,
how to create an empty generic array in Kotlin?

var items: Array<T> = ?

I wanted to use arrayOf<T>() but this doesn't work.

[Andreas Sinz]

@Erfan You need to tell the compiler what T is

[Erfan]

how do I do it?
It's not known at compile time.

[Erfan]

i.e: it could be almost any type

[Andreas Sinz]

then use Any

[rrader]

var items: Array<T> = emptyArray()

[Erfan]

it responds with Type mismatch when I try to do :

var items: Array<T> = arrayOf<Any>()

[Andreas Sinz]

you cannot use an undefined T in your code, you need to use Array<Any> = arrayOf()

[spand]

Cant you just cast it ?

[Andreas Sinz]

Array is invariant, so no

[Andreas Sinz]

your best option is to use Any and cast the items where necessary

[Erfan]

more complete code of the situation is this:

class PaginationManager<T>(var items: Array<T>,
                           var totalCount: Int,
                           val pageSize: Int,
                           var pageNumber: Int,
                           var status: PaginationStatus = PaginationStatus.WaitingForNextPageTrigger,
                           private val fetchClosure: PaginationFetchClosure<T>)

I just wanted to have default empty array for that.

Now I set an empty array of known type, in the call site.

[Erfan]

I had implemented something similar in Swift with no problem, so that's what made me wondering about something similar in Kotlin

[Andreas Sinz]

does class ...(var items: Array<T> = emptyArray(), ... work?

[spand]

class Foo<T> {
    val foo: Array<T> = Array<Any?>(0, {}) as Array<T>
}

works just fine. Its just an unchecked cast

[Andreas Sinz]

@spand in your example T is known. I was suspecting that he had a Array<T> inside a non-generic class

[diesieben07]

This comes down to: Don't use an Array<T>, use List<T>. "Because Java" array-generics behave differently than everywhere else.

[Erfan]

@Andreas Sinz nope, doesn't work

[spand]

...

[spand]

Anyways.. @diesieben07 is right

[Erfan]

thanks everyone, yes @diesieben07's right

[Erfan]

was not aware of the limitation

[Erfan]

you guys don't want to set a profile picture? 😄 I mean look at the thread.. it's a bit difficult to follow who said what.