WeakDelegate.kt

package com.marcellogalhardo.weak

import java.lang.ref.WeakReference
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty

/**
 * Creates a new instance of the [WeakDelegate] for better Kotlin
 * syntax using the [referent] parameter as an initial reference.
 *
 * Note the GC might reclaim the [referent] value before your first usage.
 */
fun <T> weak(referent: T? = null): ReadWriteProperty<Any, T?> = WeakDelegate(referent)

/**
 * Represents a [WeakReference] value - which do not prevent their referents
 * from being made finalizable, finalized, and then reclaimed.
 */
private class WeakDelegate<T>(
    private var weakReference: WeakReference<T?>?
) : ReadWriteProperty<Any, T?> {

    constructor(value: T) : this(WeakReference(value))

    override operator fun getValue(
        thisRef: Any,
        property: KProperty<*>
    ): T? = weakReference?.get()

    override operator fun setValue(
        thisRef: Any,
        property: KProperty<*>, value: T?
    ) {
        weakReference = WeakReference(value)
    }
}