Organizing objects with class

我觉得“organize objects with class”这个命题特别好。它说明白了class是一种组织工具或者组织方式而已，而不是核心的东西——核心的、基础的东西是object。

David A. Black先生说过：Defining a class lets you group behaviors (methods) into convenient bundles, so that you can quickly create many objects that behave essentially the same way. 这就说明class存在的意义是：按照某种目的把behaviors打包。
比方说：地上胡乱堆放了一堆铁钉、螺丝、图钉、胶带、创可贴、胶水。妈妈叫你把这些东西分类归置好。你会怎么分类？我会把铁钉、螺丝、图钉挑出来放一个盒子里，贴上一个标签“铁钻物”；把胶带、创可贴、胶水放到另一个盒子里，标作“粘合品”。这就是“分类”——在英语里面叫class。为啥要这样分啊？因为铁钉、螺丝、图钉有类似的行为——在英语里叫behavior，在程序里我们通常叫method。

Classes are object factories. Classes are also special objects: They’re the only kind of object that has the power to spawn new objects (instances). Nonetheless, they are objects.