Swift可用性检查不包括macOS [英] Swift availability check exclude macOS

问题描述

我的应用程序中有一个代码，希望在iOS 13或更高版本上执行.因此，我正在使用标准的可用性检查:

I have a code in my app which I want to execute on iOS 13 or later. So, I was using a standard availability check:

if #available(iOS 13.0, *) {
    return Color.systemGray6.resolvedColor(with: trait!)
} else {
    return Color(red: 0.082, green: 0.118, blue: 0.161, alpha: 1.0)
}

Color是一种类型别名，在iOS上投射为UIColor，在macOS上投射为NSColor.我正在尝试使用尽可能少的if..else创建目标的macOS版本.

Color is a typealias which casts to UIColor on iOS and NSColor on macOS. I am kind of trying to create macOS version of my target with as little if..else as possible.

上面的代码应与NSColor一样工作，具有许多与UIColor相同的初始化方法.问题是，当我构建我的macOS目标时，它会抱怨systemGray6.因此，出于我未知的原因，macOS目标通过了#available(iOS 13.0, *)检查！

The code above should work as NSColor has many of the same init methods as UIColor. The problem is that when I build my macOS target it complains about systemGray6. So, for a reason unknown to me, macOS target passes #available(iOS 13.0, *) check!

为什么会发生这种情况，如何预防呢?

Why does it happen and how can I prevent it?

推荐答案

当您使用if #available(iOS 13.0, *)时，您基本上是在说:在iOS 13.0和更高版本，以及所有其他操作系统上执行此操作 -这就是*的意思.

When you use if #available(iOS 13.0, *) you're basically saying: do this on iOS 13.0 and later, and on all other operating systems - that's what the * means.

在特定情况下，您将需要排除macOS，因为NSColor没有systemGrayX吸气剂:

In your specific case, you'll need to exclude macOS, since NSColor does not have the systemGrayX getters:

#if os(iOS)
if #available(iOS 13.0, *) {
     return Color.systemGray6
}
#endif
return Color(red: 0.082, green: 0.118, blue: 0.161, alpha: 1.0)

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