过去两个星期里，为了完成一个工作，接触到了NSObject中非常特别的两个类方法(Class Method)。它们的特别之处，在于iOS会在运行期提前并且自动调用这两个方法，而且很多对于类方法的规则（比如继承，类别(Category)）都有不同的处理。
而因为这两个方法是在程序运行一开始就被调用的方法，我们可以利用他们在类被使用前，做一些预处理工作。比如我碰到的就是让类自动将自身类名保存到一个NSDictionary中。
先来看看NSObject Class Reference里对这两个方法说明：
+(void)initialize
The runtime sends
initializeto each class in a program exactly one time just before the class, or any class that inherits from it, is sent its first message from within the program. (Thus the method may never be invoked if the class is not used.) The runtime sends the initialize message to classes in a thread-safe manner. Superclasses receive this message before their subclasses.
+(void)load
The
loadmessage is sent to classes and categories that are both dynamically loaded and statically linked, but only if the newly loaded class or category implements a method that can respond.
The order of initialization is as follows: 阅读全文 >>