Hello! Does anybody know how to declare get() & set() for delegated properties correctly ? I'v t...

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[Yevhenii Nadtochii]

Hello! Does anybody know how to declare get() & set() for delegated properties correctly ? I'v tried like this and it haven't worked out.

operator fun getValue(thisRef: Any, property: KProperty<*>): Any = properties[property.name]
        ?: throw IllegalStateException("Property ${property.name} hasn't been initialized!")

operator fun setValue(thisRef: Any, property: KProperty<*>, value: Any) {
    properties[property.name] = value
    listeners[property.name]?.invoke(value.toString())
}

[dmitriy.novozhilov]

Your code has two problems:
- since you declared Any as return type of set and value type of get you can use SharedStats only for properties of type Any
- you try to declare delegate for property with no receiver, so your set and get should take Nothing? as thisRef, not Any (since top-level properties has no receiver at all)

Correct declaration should look like this:

class SharedStatsFixed {
    operator fun <T> getValue(thisRef: Nothing?, property: KProperty<*>): T = TODO()
    operator fun <T> setValue(thisRef: Nothing?, property: KProperty<*>, value: T) {
        TODO()
    }
}

For more details check reference: https://kotlinlang.org/docs/reference/delegated-properties.html#property-delegate-requirements for

[Yevhenii Nadtochii]

@dmitriy.novozhilov thank you, it helped! does it mean I have no chance to avoid unchecked cast ? and library-implementation uses unchecked cast as well (map-properties) ?

[dmitriy.novozhilov]

Yes it is