在iOS 5应用程序中有条件地支持iOS 6功能 [英] Conditional support of iOS 6 features in an iOS 5 app

问题描述

如何在最小部署目标设置为iOS 5.0的应用中支持iOS6的功能？

How can you support features of iOS6 in an app with a Minimal Deployment Target set to iOS 5.0?

例如，如果用户拥有iOS 5，他将看到一个 UIActionSheet ，如果用户拥有iOS 6，他将看到不同的 UIActionSheet 适用于iOS 6？你怎么做到这一点？
我有Xcode 4.5，想在iOS 5上运行一个应用程序。

For example, if a user has iOS 5 he will see one UIActionSheet, if the user has iOS 6 he will see a different UIActionSheet for iOS 6? How do you do this? I have Xcode 4.5 and want an app running on iOS 5.

推荐答案

你应该总是喜欢检测可用的方法/功能而不是iOS版本，然后假设有一个方法。

You should always prefer detecting available methods/feature rather then iOS versions and then assuming a method is available.

参见 Apple文档。

例如，在iOS 5中显示一个模态视图控制器我们会这样做：

For example, in iOS 5 to display a modal view controller we would do something like this:

[self presentModalViewController:viewController animated:YES];

在iOS 6中， presentModalViewController：animated： UIViewController 的方法已弃用，你应该在iOS 6中使用 presentViewController：animated：completion：，但是你怎么做知道什么时候使用什么？

In iOS 6, the presentModalViewController:animated: method of UIViewController is Deprecated, you should use presentViewController:animated:completion: in iOS 6, but how do you know when to use what?

你可以检测到iOS版本并且如果你使用前者或后者就有一个if语句，但这很脆弱，你会做一个错误，也许未来更新的操作系统会有新的方法来实现这一目标。

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.

处理这个问题的正确方法是：

The correct way to handle this is:

if([self respondsToSelector:@selector(presentViewController:animated:completion:)])
    [self presentViewController:viewController animated:YES completion:^{/* done */}];
else
    [self presentModalViewController:viewController animated:YES];

你甚至可以说你应该更加严格，做一些事情：

You could even argue that you should be more strict and do something like:

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 !");

我不确定您的 UIActionSheet 示例，据我所知，这在iOS 5和6上是一样的。也许你想要 UIActivityViewController 进行共享，你可能想要回退到 UIActionSheet 如果您使用的是iOS 5，那么您可以查看课程是否可用，请参阅这里怎么做。

I'm unsure about your UIActionSheet example, as far as I'm aware this is the same on iOS 5 and 6. Maybe you are thinking of UIActivityViewController for sharing and you might like to fallback to a UIActionSheet if you're on iOS 5, so you might to check a class is available, see here how to do so.

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