Auto HashMappable Object with Kotlin (Thanks to Property Delegation!)

Auto_HashMappable_Object_Example.kt

class User : HashMappable() {

    var name: String by HashMappableProperty("")
    var age: Int? by HashMappableProperty(null)

}

fun main() {
    val harry = User()
    harry.name = "Harry"
    harry.age = 21

    print(harry.map) // Prints { "name" : "Harry", "age" : 21 }


    val tom = User()
    tom.name = "Tom"
    tom.age = null

    print(tom.map) // Prints { "name" : "Tom", "age" : null }
}

HashMappable.kt

abstract class HashMappable {
    var map: Map<String, Any?> = mapOf()
}

HashMappableProperty.kt

class HashMappableProperty<T>(initialValue: T) : ReadWriteProperty<HashMappable, T> {

    private var value: T = initialValue

    override fun getValue(thisRef: HashMappable, property: KProperty<*>): T {
        return value
    }

    override fun setValue(thisRef: HashMappable, property: KProperty<*>, value: T) {
        this.value = value
        thisRef.apply { map = map + (property.name to value) }
    }

}