山狮的条件类别

问题描述

Mountain Lion引入了新API ，其中一些已在项目中实现为类别.

Mountain Lion introduced new APIs, some of which we had implemented as categories in our project.

例如，我们有一个类别NSColor+CGColorAdditions，它为NSColor实现了CGColor和colorWithCGColor:.这些方法已在山狮"中添加.

For examples, we have a category NSColor+CGColorAdditions that implemented CGColor and colorWithCGColor: for NSColor. These methods have been added in Mountain Lion.

理想情况下，如果客户端操作系统早于Mountain Lion，我们希望使用这些类别，如果是Mountain Lion，则不使用它们.我们应该怎么做?还是有更好的选择?

Ideally, we would like to use these categories if the client OS is older than Mountain Lion, and not use them if it's Mountain Lion. How can we do this? Or is there a better alternative?

推荐答案

NSColor *_NSColor_colorWithCGColor_(Class self, SEL cmd, CGColorRef cgColor)
{
    // make an NSColor outta `cgColor` and return it
    return nsColor;
}

// inside some initialization code

if ([[NSColor class] respondsToSelector:@selector(colorWithCGColor:)]) {
    // on ML, don't do anything
} else {
    // older system, add your own category
    class_addMethod(objc_getMetaClass("NSColor"), @selector(colorWithCGColor:), (IMP)_NSColor_colorWithCGColor_, "@@:@");
}

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