否定objective-c的@available关键字-NegatingObjective-C's@availablekeyword

I would like to run a piece of code only if the iOS version of the current device is below a specific version, as specified here. The code examples given by Apple look like this:

我只希望在当前设备的iOS版本低于特定版本的情况下运行一段代码。苹果给出的代码示例如下:

if (@available(iOS 10.0, *)) {
  // iOS 10.0 and above
} else {
  // below 10.0
}

However, there are scenarios where one would like to run code only if the current iOS version is below a specific version. I assumed the following code will work:

但是，有些情况下，只有在当前的iOS版本低于特定版本时，才会运行代码。我假设下面的代码可以工作:

if (!@available(iOS 10.0, *)) {
  // below 10.0
}

However it seems that this doesn't work, and I'm getting the following warning from Xcode:

然而，这似乎不起作用，我得到了Xcode的以下警告:

@available does not guard availability here; use if (@available) instead

Here is the LLVM commit that added the diagnostic I'm seeing.

这里是LLVM提交，添加了我所看到的诊断。

There are two possible fallbacks to that issue:

对于这个问题有两种可能的退步:

1. Use the if-else variant without adding any code to the if block (not very elegant).
2. 使用if-else变体而不向if块添加任何代码(不是非常优雅)。
3. Continue to use old approaches such as -[NSProcessInfo isOperatingSystemAtLeastVersion:].
4. 继续使用旧的方法，例如-[NSProcessInfo isoperatingsystemat至少version:]。

Is there another intended way to use @available that I'm missing?

是否有另一种可用的方法来使用@available ?

1 个解决方案

#define isIOS11() ([[UIDevice currentDevice].systemVersion doubleValue]>= 11.0 && [[UIDevice currentDevice].systemVersion doubleValue] <12.0)

#define SinceIOS9_2 ([[UIDevice currentDevice].systemVersion doubleValue]>= 4.2 && [[UIDevice currentDevice].systemVersion doubleValue] <9.2)

if (isIOS11()) {
    // Do something for iOS 11 
} else {
    // Do something iOS Versions below 11.0
}