自定义带接收者的Lazy

gistfile1.txt

import kotlin.properties.ReadOnlyProperty
import kotlin.reflect.KProperty


private val UNINITIALIZED_VALUE = Any()

/**
 *
 * @author CY 2024-12-25
 */
class ReceiverLazy<in T, out V>(private val initializer: T.() -> V) : LazyProperty<T, V> {

    private val lock = Any()

    private var _value: Any? = UNINITIALIZED_VALUE

    override fun getValue(thisRef: T, property: KProperty<*>): V {

        val v1 = _value
        if (v1 != UNINITIALIZED_VALUE) {
            return v1 as V
        }

        return synchronized(lock) {
            val v2 = _value
            if (v2 != UNINITIALIZED_VALUE) {
                v2 as V
            } else {
                val typedValue = initializer(thisRef)
                _value = typedValue
                typedValue
            }
        }

    }
}

interface LazyProperty<in T, out V> : ReadOnlyProperty<T, V>

/**
 * Receiver lazy
 *
 * @param T
 * @param V
 * @param initializer
 * @receiver
 * @return
 */
fun <T, V> receiverLazy(initializer: T.() -> V): LazyProperty<T, V> =
    ReceiverLazy(initializer)