Kotlin check if data class properties are all null

Question

Suppose I have a data class with nullable properties:

data class User(
   val fName: String?,
   val lName: String?)

In a function where I receive an instance of such a class even if the instance is not null I want to check that at least one of the properties inside is initialized and not null. I know that I can check the properties one by one, but I want to have something more generic, I googled and seems Kotlin there is no extension function for this so I implemented one and would like to share with you and check if anyone knows better ways.

Andranik · Accepted Answer · 2020-06-24 07:45:50Z

8

So this can be done using Kotlin reflection and here is an extension function to do this:

fun Any.isAllNullInside(): Boolean {
     if(this::class.declaredMemberProperties.any { !it.returnType.isMarkedNullable }) return false
     return this::class.declaredMemberProperties.none { it.getter.call(this) != null }
}

@gidds thanks for a good catch. I understand that it will perform worse, but any solution based on reflection will perform worse than if it will be done by hand. But if it's fine to loose some small performance but have generic solution I guess reflection is very powerful mechanism.

Related to the non nullable properties and lateinit vars, I have added a line of code which fixes both. Thanks for a catch!

edited Jun 24, 2020 at 7:45

answered Jun 24, 2020 at 6:54

Andranik

2,8591 gold badge33 silver badges49 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

gidds Over a year ago

Note that using reflection like this is likely to perform much worse than explicit checks. (It also checks non-nullable properties as well -- pointlessly. And you should confirm that it works for lateinit properties, and doesn't throw an exception instead of returning false.)

Collectives™ on Stack Overflow

Kotlin check if data class properties are all null

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related