A Ruby hash (or associative array) is a data structure that allows you to define the key for storage (instead of a simple numerical index).
Ruby散列表(或关联数组)是一种数据结构，允许您定义用于存储的键(而不是简单的数值索引)。
To represent the above foreign key relationship in Ruby on Rails, you will have to create an association between the models.
你需要在模型之间创建关联才能够在Ruby on Rails中表示外键。
But for all the diversity of Ruby on Rails applications, the ones that are best-suited to the framework have a few key things in common.
但是这么多不同的Ruby on Rails应用程序，有几个重要的共通最适关键。
应用推荐