Hi guys, is it possible to get type from Any? I ne...

# announcements

[Timur Atakishiev]

Hi guys, is it possible to get type from Any? I need to check whether Any is Collection<String>. I tried something like

inline fun <reified T> isTypeOf(any: Any?): Boolean {
    return any is T
}

val isTypeOf: Boolean = isTypeOf<Collection<String>>(Any)

my Any is ArrayList of String.

[diesieben07]

Generics are erased, so at runtime there is no way to distinguish a List<String> from a List<Any>, there is only List.

[Timur Atakishiev]

kotlins reified will not help me either?

[diesieben07]

I don't think so, because they don't allow you to "unpack" the type (i.e. go from List<String> to String). But I could be wrong on that.

[Vampire]

Just see here: https://pl.kotl.in/UFFqLrmzK

[Vampire]

println(arrayListOf(Object()) is Collection<String>) will give compiler error Cannot check for instance of erased type: Collection<String>

[Vampire]

So if it does not work directly, it will most probably not work reified

[Timur Atakishiev]

Thank you!

[Vampire]

Or actually see here: https://pl.kotl.in/jvhB1whOt

[Vampire]

Due to the reified type usage the compiler is not smart enough to error out

[Vampire]

So it compiles fine, but it returns true

[Vampire]

Because erased types are checked

[Timur Atakishiev]

@Vampire The only way is to iterate through Collection and check whether element is String, am I right?

[Vampire]

That could maybe work, yes

[diesieben07]

That would only tell you if there are strings in the collection. It could still be created as `Collection<Any>`:

val collection: MutableCollection<Any> = listOf("Hello World")
val isStringCollection = collection.all { it is String } // true, even though it's not