ios - 用于了解 Xcode 4.3.2 中是否启用 ARC 的宏

Question

在同一个文件中，我们要编写支持 ARC 和非 ARC 的代码。为此需要一些宏。

#ifdef ARC_ENABLED 
NSLog(@" ARC enabled ");
#else
NSLog(@" ARC disabled ");
[self release];
#endif

如何实现这个宏，有没有什么宏可用？ 请告诉我。先谢谢支持 注意:ARC_ENABLED 只是我写的例子

Answer 1

有一个 Objective-C 宏 __has_feature，您可以使用它来检查是否启用了 arc。

来自 Clang Language Extension documentation

Automatic reference counting

Clang provides support for automated reference counting in Objective-C, which eliminates the need for manual retain/release/autorelease message sends. There are two feature macros associated with automatic reference counting: __has_feature(objc_arc) indicates the availability of automated reference counting in general, while __has_feature(objc_arc_weak) indicates that automated reference counting also includes support for __weak pointers to Objective-C objects.

本节Feature checking macro's是一本非常好的读物。

你可以像这样使用它..

#if !__has_feature(objc_arc)
    //Do manual memory management...
#else
    //Usually do nothing...
#endif

代码部分无耻地抄自this answer .