转自:http://developer.apple.com/library/mac/#releasenotes/Cocoa/RN-ObjectiveC/_index.html
@packageis a new instance variable protection class, like@publicand@protected.@packageinstance variables behave as follows:
-
@publicin 32-bit; -
@publicin 64-bit, inside the framework that defined the class; -
@privatein 64-bit, outside the framework that defined the class.
In 64-bit, the instance variable symbol for an@packageivar is not exported, so any attempt to use the ivar from outside the framework that defined the class will fail with a link error. See "“64-bit Class and Instance Variable Access Control”" for more about instance variable symbols.
本文深入探讨了 Objective-C 中 @package 属性的行为,包括在 32 位和 64 位环境下的作用及实例变量的访问控制。

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