So it doesn't matter how big the dictionary is, you can instantaneously retrieve the value associated with the key. Extremely powerful.

因为你可以在线性时间，内得到想要的键对应的值,这太强大了。

麻省理工公开课 - 计算机科学及编程导论课程节选

Remember the way dictionary works, this is the key. Is the key of a value.

记住这个字典的工作原理，这是关键，它是值的关键。

麻省理工公开课 - 计算机科学及编程导论课程节选

Inside the dictionary should be the UINavigationBar key, which has a value that is also a dictionary.

ENGADGET: Apple seeds iOS 6 beta 4 to developers: here's the changelog

The value of this key is a dictionary with the appropriate values describing the navigation bar your app has at startup.

ENGADGET: Apple seeds iOS 6 beta 4 to developers: here's the changelog