xcode 有条件地支持 iOS 5 应用程序中的 iOS 6 功能
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/12589866/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Conditional support of iOS 6 features in an iOS 5 app
提问by Sergey Grischyov
How can you support features of iOS6 in an app with a Minimal Deployment Targetset to iOS 5.0?
如何在Minimal Deployment Target设置为 iOS 5.0的应用程序中支持 iOS6 的功能？
For example, if a user has iOS 5 he will see one UIActionSheet, if the user has iOS 6 he will see a different UIActionSheetfor iOS 6? How do you do this?
I have Xcode 4.5 and want an app running on iOS 5.
例如，如果用户有 iOS 5，他会看到一个UIActionSheet，如果用户有 iOS 6，他会看到UIActionSheetiOS 6的不同吗？你怎么做到这一点？我有 Xcode 4.5 并且想要一个在 iOS 5 上运行的应用程序。
回答by Daniel
You should always prefer detecting available methods/feature rather then iOS versions and then assuming a method is available.
你应该总是更喜欢检测可用的方法/功能而不是 iOS 版本，然后假设一个方法可用。
See Apple documentation.
请参阅Apple 文档。
For example, in iOS 5 to display a modal view controller we would do something like this:
例如，在 iOS 5 中要显示一个模态视图控制器，我们会做这样的事情：
[self presentModalViewController:viewController animated:YES];
In iOS 6, the presentModalViewController:animated:method of UIViewControlleris Deprecated, you should use presentViewController:animated:completion:in iOS 6, but how do you know when to use what?
在 iOS 6 中，presentModalViewController:animated:方法UIViewController是 Deprecated，你应该presentViewController:animated:completion:在 iOS 6 中使用，但是你怎么知道什么时候使用什么？
You could detect iOS version and have an if statement dictate if you use the former or latter but, this is fragile, you'll make a mistake, maybe a newer OS in the future will have a new way to do this.
您可以检测 iOS 版本并使用 if 语句来指示您是使用前者还是后者，但是，这很脆弱，您会犯错，也许将来更新的操作系统会有新的方法来做到这一点。
The correct way to handle this is:
正确的处理方法是：
if([self respondsToSelector:@selector(presentViewController:animated:completion:)])
[self presentViewController:viewController animated:YES completion:^{/* done */}];
else
[self presentModalViewController:viewController animated:YES];
You could even argue that you should be more strict and do something like:
您甚至可以争辩说您应该更严格并执行以下操作：
if([self respondsToSelector:@selector(presentViewController:animated:completion:)])
[self presentViewController:viewController animated:YES completion:^{/* done */}];
else if([self respondsToSelector:@selector(presentViewController:animated:)])
[self presentModalViewController:viewController animated:YES];
else
NSLog(@"Oooops, what system is this !!! - should never see this !");
I'm unsure about your UIActionSheetexample, as far as I'm aware this is the same on iOS 5 and 6. Maybe you are thinking of UIActivityViewControllerfor sharing and you might like to fallback to a UIActionSheetif you're on iOS 5, so you might to check a class is available, see herehow to do so.
我不确定你的UIActionSheet例子，据我所知，这在 iOS 5 和 6 上是一样的。也许你正在考虑UIActivityViewController分享，UIActionSheet如果你在 iOS 5 上，你可能想回退到一个，所以你可能会检查类是否可用，请参阅此处如何操作。
