How to check if a variable is an array in Kotlin

Question

My Kotlin code is

val t = cameraController.getCharacteristicInfo(myDataset[position])
if (t is Array<*>) {
     holder.keyValue.text = Arrays.toString(t)
} else {
     holder.keyValue.text = t.toString()
}

It is not working. if (t is Array<*>) always returns false.

The code of the function getCharacteristicInfo is:

public <T> T getCharacteristicInfo(CameraCharacteristics.Key<T> key) {
    return characteristics.get(key);
}

It is a function for getting camera characteristics.

How to properly check if a variable is an array?

Ok. Added it. It it a function getting camera characteristics. — Aaron Lee
– Aaron Lee, Commented Feb 20, 2019 at 9:50
It seems t is not actually Array type. Could you edit your code to show type of characteristics and myDataset[position] as well? — Son Truong
– Son Truong, Commented Feb 20, 2019 at 10:01
Can you show the type of myDataset[position] variable? getCharacteristicInfo returns value of type T related to Key<T> being passed as parameter. myDataset[position] is some kind of Key<T> (indeed, the code compiles) but may be is - e.g. - Key<String> and this forces t to be of type String... — Pietro Martinelli
– Pietro Martinelli, Commented Feb 20, 2019 at 14:40

Alexey Romanov · Accepted Answer · 2019-02-20 17:03:03Z

11

t is Array<*> is true for object arrays (Array<Whatever>), but false for primitive arrays (IntArray etc.). So you probably want

holder.keyValue.text = when(val t = cameraController.getCharacteristicInfo(myDataset[position])) {
    is Array<*> -> Arrays.toString(t)
    is IntArray -> Arrays.toString(t)
    ...
    else -> t.toString()
}

(if t is used outside elsewhere, just move the assignment outside).

Note that these are different Arrays.toString overloads, so you couldn't write

is Array<*>, is IntArray, ... -> Arrays.toString(t)

even if smart casts were available in this situation (they aren't).

answered Feb 20, 2019 at 17:03

Alexey Romanov

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Aleksander Stelmaczonek · Accepted Answer · 2019-10-20 20:20:21Z

1

Faced the same issue and used isArray of the Class:

>>> arrayOf("a","b","c")::class.java.isArray
res1: kotlin.Boolean = true
>>> IntArray(1)::class.java.isArray
res2: kotlin.Boolean = true
>>> Array<String>(1) { "a" }::class.java.isArray
res3: kotlin.Boolean = true
>>> Any::class.java.isArray
res4: kotlin.Boolean = false

NOTE: That might not be available if your target is not JVM.

answered Oct 20, 2019 at 20:20

Aleksander Stelmaczonek

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