Is there any way to have a setter for a variable d...

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[nulldev]

Is there any way to have a setter for a variable declared in the constructor? I have a data class where I must have a setter for one of the fields. Example:

data class WTF(var name: String
                                  set(value) {
                                      println("This doesn't work 😞")
                                  }
                           )

[Ruckus]

Arguably that's not a data class, as it does more than just wrap data. Once you need to customize functionality, it's worth reconsidering if the data modifier still applies.

[nulldev]

Doesn't data class just auto-implement equals, hashCode, toString and a copy function?

This particular class is in an API. I have to check if the values provided to the setter are valid and throw an exception if they are not.

[Ruckus]

It does a few other things as well, but what it does is not the same as its purpose. From the docs:

We frequently create classes whose main purpose is to hold data. In such a class some standard functionality and utility functions are often mechanically derivable from the data. In Kotlin, this is called a data class ...

(see https://kotlinlang.org/docs/reference/data-classes.html)
If you are changing how the data is set or retrieved, you're probably breaking the "mechanically derivable standard functionality" point of data classes.

[gps]

I ran into a similar problem not too long ago. Ended up not using data classes. Wrote it up: http://gopalkri.com/2017/08/15/Kotlin-Data-Class-Constructor-Problem/ and http://gopalkri.com/2017/08/18/Kotlin-Data-Class-Constructor-Problem-Followup/

[gjesse]

could you override copy() ?

[gjesse]

no, i guess not