如何在Swift中实现可选值? [英] How are optional values implemented in Swift?

问题描述

我想知道Swift中的值类型(Int，Float ...)如何实现以支持可选绑定(?"). 我假设这些值类型不是分配在堆上，而是分配在栈上.那么，它们是否依赖于指向可能为null的堆栈的指针，或者底层结构是否包含布尔标志?

I wonder how the value types in Swift (Int, Float...) are implemented to support optional binding ("?"). I assume those value types are not allocated on the heap, but on the stack. So, do they rely on some kind of pointer to the stack that may be null, or does the underlying struct contain a boolean flag ?

推荐答案

在Swift中，可选项以enum类型实现.

Optionals are implemented as enum type in Swift.

请参见 Apple的Swift Tour 有关如何完成此操作的示例:

See Apple's Swift Tour for an example of how this is done:

enum OptionalValue<T> {
    case None
    case Some(T)
}

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