CODEWITHSUNDEEP
inheritancekotlindata-class
Yarick
Yarick

Reputation: 346

Kotlin: How to inherit property in data class

I have abstract Token class declared like this:

abstract class Token(var index: Int = 0) {
open fun merge(toMerge: Token): Token? {
    return null
    }
}

I want to inherit index property in data class, like this:

data class CloseLoop(index: Int, var openLoopIndex: Int = 0) : Token(index)

But it gives me error Data class primary constructor must have only property (val / var) parameters

What i have to do to fix this?

Upvotes: 8

Views: 9563

Answers (1)

hotkey
hotkey

Reputation: 147911

There are at least two workarounds:

  • Make the property open and override it in the data class primary constructor declaration:

    abstract class Token(open var index: Int = 0)

data class CloseLoop(
    override var index: Int, 
    var openLoopIndex: Int = 0
) : Token(index)

  • Declare a property with another name and initialize the base class with it:

    data class CloseLoop(val theIndex: Int, var openLoopIndex: Int = 0) : Token(theIndex)

    Make it private if you find it appropriate.

Upvotes: 21

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