Objective-c为旧设备添加对新类的支持 [英] Objective-c add support for new classes to old devices

问题描述

问题：每个新iOS都会添加许多新的有用类。例如，UIRefreshControl。我想在iOS5版本中添加对这个类的支持。

The problem: every new iOS adds a lot of new useful classes. For example, UIRefreshControl. I want to add support for this class in iOS5 build.

不酷的解决方案：在所有必须使用UIRefreshControl的类中，我可以检查当前iOS版本并使用内联替换该类，例如：

Not cool solution: In all classes that must use UIRefreshControl, I can check for current iOS version and use inline replacement for that classes, for example:

pseudocode
...

- (void)viewDidLoad
{
    ...

    if([[UIDevice currentDevice].systemVersion floatValue] < 6.0)
    {
        self.refreshControl = [[MyCustonRefreshControl_for_iOS5 alloc] init];
    }
    else
    {
        self.refreshControl = [[UIRefreshControl alloc] init];
    }
    ...
}

此解决方案是'很酷，因为我必须在我想要使用最新iOS功能的所有类中添加相同的代码。

This solution is't cool, because I must add same code in all classes where I want to use latest iOS features.

可能很酷的解决方案：
1）获取或创建自己的100％兼容类，例如对于UIRefreshControl，您可以使用CKRefreshControl（https://github.com/instructure/CKRefreshControl）;
2）使用Objective-C运行时在App启动时将替换类定义为主类。

Possible cool solution: 1) get or create your own 100% compatible class, for example for UIRefreshControl you can use CKRefreshControl (https://github.com/instructure/CKRefreshControl); 2) use Objective-C runtime to define replacement class as main class when App starts.

pseudocode
...

// ios 5 compatibility
#include <objc/runtime.h>
#import "CKRefreshControl.h"
...



- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    ...

    // pre-ios 6 compatibility
    if([[UIDevice currentDevice].systemVersion floatValue] < 6.0)
    {
        // register refresh control
        Class clazz = objc_allocateClassPair([CKRefreshControl class], "UIRefreshControl", 0);
        objc_registerClassPair(clazz);
    }

    ...
}

我认为这种方式真的很酷，但这段代码不起作用。

I think that this way is really cool, but this code won't work.

推荐答案

@abuharsky，[CKRefreshControl] https://github.com/instructure/CKRefreshControl 已更新，现在可以满足您的要求。您需要做的就是：

@abuharsky, [CKRefreshControl]https://github.com/instructure/CKRefreshControl has been updated and now does exactly what you are asking for. All you need to do is:

self.refreshControl = [[UIRefreshControl alloc] init];

如果这不适合你，请告诉我们。

Let us know if that doesn't work for you.

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