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package ca.allanwang.kau.kotlin
import java.io.Serializable
import kotlin.reflect.KProperty
/**
* Created by Allan Wang on 2017-05-30.
*
* Lazy delegate that can be invalidated if needed
* https://stackoverflow.com/a/37294840/4407321
*/
internal object UNINITIALIZED
fun <T : Any> lazyResettable(initializer: () -> T): LazyResettable<T> = LazyResettable<T>(initializer)
class LazyResettable<T : Any>(private val initializer: () -> T, lock: Any? = null) : ILazyResettable<T>, Serializable {
@Volatile
private var _value: Any = UNINITIALIZED
private val lock = lock ?: this
override fun invalidate() {
_value = UNINITIALIZED
}
override val value: T
get() {
val _v1 = _value
if (_v1 !== UNINITIALIZED)
@Suppress("UNCHECKED_CAST")
return _v1 as T
return synchronized(lock) {
val _v2 = _value
if (_v2 !== UNINITIALIZED) {
@Suppress("UNCHECKED_CAST")
_v2 as T
} else {
val typedValue = initializer()
_value = typedValue
typedValue
}
}
}
override fun isInitialized(): Boolean = _value !== UNINITIALIZED
override fun toString(): String = if (isInitialized()) value.toString() else "Lazy value not initialized yet."
operator fun setValue(any: Any, property: KProperty<*>, t: T) {
_value = t
}
}
interface ILazyResettable<out T> : Lazy<T> {
fun invalidate()
}
interface ILazyResettableRegistry {
fun <T : Any> lazy(initializer: () -> T): LazyResettable<T>
fun <T : Any> add(resettable: LazyResettable<T>): LazyResettable<T>
fun invalidateAll()
fun clear()
}
/**
* The following below is a helper class that registers all resettables into a weakly held list
* All resettables can therefore be invalidated at once
*/
class LazyResettableRegistry : ILazyResettableRegistry {
var lazyRegistry: MutableList<LazyResettable<*>> = mutableListOf()
override fun <T : Any> lazy(initializer: () -> T): LazyResettable<T> = add(lazyResettable(initializer))
override fun <T : Any> add(resettable: LazyResettable<T>): LazyResettable<T> {
lazyRegistry.add(resettable)
return resettable
}
override fun invalidateAll() = lazyRegistry.forEach { it.invalidate() }
override fun clear() = lazyRegistry.clear()
}
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