I know it's possible to do

class Blah(val map: Map<String, Any>) {
    val value1: String by map
    val value2: String by map
    val value3: Boolean by map
}

and now I can do

val blah = Blah(mapOf("value1" to "...", ...)); 

println(blah.value1)
println(blah.value2)
println(blah.value3)

wouldn't it be cool if you could do

data class Blah(
        val value1: String,
        val value2: String,
        val value3: Boolean,
    ) {

        constructor(map: Map<String, Any>): this(
            value1 by map,
            value2 by map
            value3 by map
        )
    }

now I can do

Blah(map).copy(value3 = ...)

Just a random thought ...

The thing is, in the original

Blah

, every time you access a value in Blah, you're actually doing a lookup in the map. In your proposed data class constructor, how would you implement it so that there is only one map but you have two instances of Blah with different values?

You'll need two classes probably The second example, I'm hoping to once-off copy the values from the map via map delegates which would effectively be

data class Blah(
        val value1: String,
        val value2: String,
        val value3: Boolean,
    ) {

        constructor(map: Map<String, Any>): this(
            value1 = map["value1"],
            value2 = map["value2"],
            value3 = map["value3"],
        )
    }

but

by

doesn't seem to work in that context

class BlahFromMap(map: Map<String, Any>)

and then class Blah with a second constructor which takes BlahFrom map as a type and then manually copying data over Probably something that can be solved with KSP to generate helper classes that can be instantiated from a Map ... or I could just use Serialization 😄