How to make attributes in data class non null in kotlin

Question

I have a data class in Kotlin - where there are 5-6 fields,

data class DataClass(
    val attribute1: String?,
    val attribute2: String?,
    val attribute3: Boolean?
)

i can initialise the class with DataClass(attribute1="ok", attribute2=null, attribute3= null)

Is there any way to prevent null values in data class ?

The point of ? is to allow null values, so just remove it. — Alexey Romanov
– Alexey Romanov, Commented Jul 24, 2019 at 12:32
var attribute2: String = "", var attribute3: Boolean = false, like this? — Alexandr Kolesnik
– Alexandr Kolesnik, Commented Jul 24, 2019 at 12:33

ordonezalex · Accepted Answer · 2019-07-25 15:33:43Z

1

Kotlin's type system uses ? to declare nullability. Your data class has fields which are nullable. You can prevent them from being null by removing the ? from their types:

data class DataClass(
    val attribute1: String, // not `String?`
    val attribute2: String, // not `String?`
    val attribute3: Boolean // not `Boolean?`
)

fun main() {
    // This line will compile
    val tmp = DataClass(attribute1 = "", attribute2 = "", attribute3 = false)

    // This line will not compile
    val fail = DataClass(attribute1 = null, attribute2 = null, attribute3 = null)
}

edited Jul 25, 2019 at 15:33

answered Jul 24, 2019 at 17:39

ordonezalex

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