How to initiate a fixed size array in data class

Question

I tried to research it but didn't find an answer. I'm creating a data class and in that class I would like to create an array with a fixed size. I tried the following 3 options:

data class User (
    val profilePics = arrayOf("a", "b", "c")
)

data class User (
    val profilePics: Array<String>(3)
)

data class User (
    val profilePics = arrayOfNulls<String>(3)
)

But none of them work. This does work however:

data class User (
    val profilePics: Array<String>
)

How can I initialize a fixed-size strings array inside a data class

Does this answer your question? What's the Kotlin equivalent of Java's String[]? — Ori Marko
– Ori Marko, Commented Dec 24, 2019 at 9:41
When you are trying to make fixed size array, there is possibility you don't need array at all - just make 3 separate fields. — Ircover
– Ircover, Commented Dec 24, 2019 at 10:50
Also note that arrays in a data class' primary constructor properties are compared by reference during the equality checks, not by content. For that reason, you may want to use a collection or a custom data structure instead of an array. — hotkey
– hotkey, Commented Dec 24, 2019 at 17:12

Robby Cornelissen · Accepted Answer · 2019-12-24 09:47:59Z

1

You need type annotations on your value parameters.

The following two will compile just fine:

data class User (
    val profilePics: Array<String> = arrayOf("a", "b", "c")
)

data class User (
    val profilePics: Array<String?> = arrayOfNulls<String>(3)
)

Of course, nothing prevents the caller from passing in differently sized arrays when creating instances of any of these data classes:

val user = User(arrayOf("a", "b", "c", "d")) // compiles fine

edited Dec 24, 2019 at 9:47

answered Dec 24, 2019 at 9:39

Robby Cornelissen

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1 Comment

sir-haver Over a year ago

Thank you very much Robby it's working and it's interesting to know that you can pass different sizes

Khalid Saeed · Accepted Answer · 2019-12-24 09:58:39Z

1

Use this :

var list:ArrayList <String> = ArrayList(5)

edited Dec 24, 2019 at 9:58

answered Dec 24, 2019 at 9:35

Khalid Saeed

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1 Comment

sir-haver Over a year ago

Thanks Khalid it's working now I upvoted your answer

Dipankar Baghel · Accepted Answer · 2019-12-24 10:10:09Z

1

try this - hope this help var array = Array(2){i ->1}

or

var array = arrayOf(1,2,3) // you can increase the size too

answered Dec 24, 2019 at 10:10

Dipankar Baghel

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