ios - Kotlin / native : Can someone help me in suggesting how to create a frozen singleton that takes in init parameters?

Question

下面的代码将不起作用，因为一旦我们尝试像 SomeClass.getInstance() 或它的任何其他属性一样访问它，就会创建伴随对象并使其不可变，我不会能够初始化 someClass 属性。我希望它是不可变的/卡住的(因为这将从多个线程访问)但是当它需要参数时我不能这样做。

有什么建议吗？

actual open class SomeClass private constructor(private val someProperty: SomeProperty) {
    actual companion object {
        private var someClass: SomeClass? = null
        fun initialize(someProperty: SomeProperty){
            someClass = SomeClass(someProperty)
        }
        actual fun getInstance(): SomeClass {
            if (someClass == null) {
                throw UninitializedPropertyAccessException("SomeClass is not initialised yet")
            }
            return someClass as SomeClass
        }
    }
}

一种可能的解决方案是在此处使用 AtomicReference。像这样:

actual open class SomeClass private constructor(private val someProperty: SomeProperty) {
    actual companion object {
        private var someClassAtomicRef: AtomicReference<SomeClass?> = AtomicReference(null)
        fun initialize(someProperty: SomeProperty){
            val someClass = SomeClass(someProperty)
            someClassAtomicRef.value = someClass.freeze()
        }
        actual fun getInstance(): SomeClass {
            return someClassAtomicRef.value ?: throw UninitializedPropertyAccessException("SomeClass is not initialised yet")
        }
    }
}

上面代码的问题是我可以再次调用 SomeClass.initialise 并在 AtomicReference 中有另一个 SomeClass 实例。

有没有更好的方法来实现这一目标？

Answer 1

Atomic Reference 是通往这里的路

actual open class SomeClass private constructor(private val someProperty: SomeProperty) {
    actual companion object {
        private var someClassAtomicRef: AtomicReference<SomeClass?> = AtomicReference(null)
        fun initialize(someProperty: SomeProperty){
            val someClass = SomeClass(someProperty)
            someClassAtomicRef.compareAndSet(null, someClass.freeze())
        }
        actual fun getInstance(): SomeClass {
            return someClassAtomicRef.value ?: throw UninitializedPropertyAccessException("SomeClass is not initialised yet")
        }
    }
}