Is it possible to instantiate a data class with dy...

# reflect

[lazt omen]

Is it possible to instantiate a data class with dynamic properties. Let's say I have this.

data class Business(
    val id: Int,
    val name: String
)

val columns = listOf("id", "name")
val values = listOf(1, "Hello")

Is it possible to instantiate this class mapping dynamically my columns to contructor parameters?

[ephemient]

val cons = Business::class.primaryConstructor!!
val params = columns.map { name ->
    cons.parameters.single { it.name == name }
}
val business = cons.callBy(params.zip(values).toMap())

this does not check for multiple constructors, missing parameters, mismatched types, but may be enough to get you started

[lazt omen]

It totally works awesome thanks a lot.

[DALDEI]

If you can control the source for the data class you can achive this by property delegation:

data class Business( private val _data : Map<String,Any> ) {
val id : Int by _data
val name : String by _data
}

val m = columns.zip( values ) { a,b -> a to b }.toMap())
val v = Business(m)

[ephemient]

that's potentially unsafe, as

Business(mapOf())

doesn't fail at construction time, but at some later point in time when the properties are accessed, and loses other features of data classes like copy

[ephemient]

you could write

data class Business(val id: Int, val name: String)
fun Business(data: Map<String, Any>): Business? {
    return Business(
        data["id"] as? Int ?: return null,
        data["name"] as? String ?: return null,
    )
}

if you want that interface without reflection