kotlin - Is there any way to declare a scope extension to third party library kotlin class?

Question

I'm trying a program build with Jetbrain/Exposed as ORM library and TornadoFX which is a kotlin version wrapper of JavaFX as UI Framework. There is a problem that an entity's class property is delegated by Exposed.

object Paintings: UUIDTable() {
    ...
    val description = text("description").default("")
    ...
}

class Painting(id: EntityID<UUID>) : UUIDEntity(id) {
    ...

    var description by Paintings.description

    ...
}

And I'm also want to create an property delegated to JavaFX's property like this

class Painting(id: EntityID<UUID>) : UUIDEntity(id) {
    ...

    var description by property<String>()
    fun descriptionProperty() = getProperty(Painting::description)

    ...
}

There is a conflict here,so I'm trying to build a own delegate class to wrapper two framework's delegated.Maybe build something which can wrap two frameworks's delegate though a infix function extension.

class Painting(id: EntityID<UUID>) : UUIDEntity(id) {
    ...

    var description by Paintings.description notify property<String>()
    fun descriptionProperty() = getProperty(Painting::description)

    ...
}

And here is the problem that the operator setValue and getValue for delegate from Exposed is declare in Entity class

open class Entity<ID:Comparable<ID>>(val id: EntityID<ID>) {
    ...

    operator fun <T> Column<T>.getValue(o: Entity<ID>, desc: KProperty<*>): T = 
        lookup()

    operator fun <T> Column<T>.setValue(o: Entity<ID>, desc: KProperty<*>, value: T) {...}

If I declare a wrapper class it just cannot access the delegate operator for Column which is scoped in Entity class

//Global Extension instead of scoped to `Entity`
infix fun <T> Column<T>.notify(fxProperty: PropertyDelegate<T>) {
    return DelegateWrapper(this,fxProperty)
}

class DelegateWrapper<T>(val column: Column<T>, val fxProperty: PropertyDelegate<T>) {

    operator fun getValue(thisRef: Any?, property: KProperty<*>): String {
        return column.getValue(...)  <-cannot resolve getValue
    }

    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: String) 
    {
        ...
    }
}

As a work arround I guess I had to build a subclass of UUIDEntity and add those extension as member extension and nest class to make it work.

Answer 1

You can do that by limiting the type that the delegate can be used with to Entity.

This can be done by replacing thisRef: Any? with thisRef: Entity<ID> and calling the getValue extension in a thisRef.run { ... } block that provides an Entitiy<ID> receiver as follows:

class DelegateWrapper<T>(val column: Column<T>, val fxProperty: PropertyDelegate<T>) {

    operator fun <ID : Comparable<ID>> getValue(
        thisRef: Entity<ID>,  // <-- here
        property: KProperty<*>
    ): String =
        thisRef.run { column.getValue(thisRef, property) }  

    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: String) = TODO()
}