A modified version of Kotlin's lazy delegate that can be reset.

Cached.kt

/**
 * Created by Brian Parma on 2/10/16.
 *
 * This is basically just the lazy delegate copy and pasted, then modified so that it can be
 * reset by setting it equal to null
 */
/**
 * Represents a value with lazy initialization.
 *
 * To create an instance of [Cached] use the [cached] function.
 */
interface Cached<T> {
    /**
     * Gets the lazily initialized value of the current Cached instance.
     * Once the value was initialized it must not change during the rest of lifetime of this Cached instance.
     */
    var value: T?
    /**
     * Returns `true` if a value for this Cached instance has a value, and `false` otherwise.
     */
    fun isCached(): Boolean
}

//@kotlin.jvm.JvmVersion
fun <T> cached(initializer: () -> T): Cached<T> = SynchronizedCachedImpl(initializer)

//@kotlin.internal.InlineOnly
inline operator fun <T> Cached<T>.getValue(thisRef: Any?, property: KProperty<*>): T? = value
inline operator fun <T> Cached<T>.setValue(thisRef: Any?, property: KProperty<*>, new_value: T?) { value = new_value }

private class SynchronizedCachedImpl<T>(initializer: () -> T, lock: Any? = null) : Cached<T>, Serializable {
    private var initializer: (() -> T)? = initializer
    @Volatile private var _value: Any? = null
    // final field is required to enable safe publication of constructed instance
    private val lock = lock ?: this

    override var value: T?
        set(new_value) {
            synchronized(lock){
                _value = new_value
            }
        }
        get() {
            val _v1 = _value
            if (_v1 !== null) {
                return _v1 as T
            }

            return synchronized(lock) {
                val _v2 = _value
                if (_v2 !== null) {
                    _v2 as T
                }
                else {
                    val typedValue = initializer!!()
                    _value = typedValue
//                    initializer = null
                    typedValue
                }
            }
        }

    override fun isCached(): Boolean = _value !== null

    override fun toString(): String = if (isCached()) value.toString() else "Cached value is not set yet."

//    private fun writeReplace(): Any = InitializedLazyImpl(value)
}