var

Cached<T : Any>

T

class CacheDelegate<T : Any>(private var initialValue: T? = null, private val factory: () -> T) {

    operator fun getValue(owner: Any, property: KProperty<*>) : T {
        if (initialValue == null) {
            initialValue = factory()
        }
        return initialValue!!
    }

    operator fun setValue(owner: Any, property: KProperty<*>, value : T)  {
        initialValue = value
    }
    
    fun invalidate() {
        initialValue = null
    }
}

class TestClass(
    testValueDel : CacheDelegate<Int>
)  {
    var testValue: Int by testValueDel
}

fun main() {
    val delegate = CacheDelegate {
        4
    }
    val testClass = TestClass(delegate)

    
    val x = testClass.testValue
    
    testClass.testValue = 234

    ...
    
    delegate.invalidate()
}

var dirtyFlag: Boolean

TestClass

CacheDelegate

TestClass

TestClass

CacheDelegate

get()

set(value)

lazy