分类话题，如何组织最有效？
以 Ruby China 源代码为基础，假设欲以 Topic 为基础，拓展开来：电影、书籍、游戏三类 Topic (除了:title 和:body 等共有属性外，还有一些特别属性，例如电影会有导演、主演、片长等属性)。以下有几种方案：
如果使用前两种方案，有没有可能使用:after_create 或:after_save 来设置"_type"值。
方法一：单表继承 (最简单)
class Movie < Topic
...
end
class MoviesController < TopicsController
...
end
方法二：共有属性单表继承，再 referenced 或 embeded 特别属性
class Movie < Topic
has_one movie_profile
...
end
class MovieProfile
belongs_to movie
...
end
class MoviesController < TopicsController
...
end
方法三：不使用类继承，把类别作为属性 (例如：:category)，共用一表
class Movie
...
field :category, :type => :string
...
end
方法四：不使用类继承，把类别作为属性 (例如：:category)，共有属性一表，再 referenced 或 embeded 分别储存
class Movie
...
field :category, :type => :string
embeds movie_profile
...
end
class MovieProfile
...
embeded_in movie
...
end
这四种方案，哪种方案最优？各有什么优缺点？
Similar Question and Solutions on StackOverFlow
####Question: Model inheritance and model specific code in the controller/view
I am using Rails single-table inheritance with a superclass Content and a number of subclasses (such as Article, Comment etc.) I am trying to get away with a single controller, and I have set up the routes thusly:
resources :contents
resources :articles, :controller => "contents"
resources :comments, :controller => "contents"
This way, /articles/new gets routed to contents#new which seems to be what I want.
Within the controller and the views, however, I need to tailor the functionality a bit depending on which actual model I am dealing with. For that purpose, I need to determine the original requested resource or otherwise find out which subclass I am dealing with.
Looking at params for /articles/newwithin the common controller gives {"action"=>"new", "controller"=>"contents"}, which obviously does not provide the information I need.
Either the answer is really obvious or I am using model inheritance wrong. Which one is it? :)
####Answer 1: You can extract the part of the request path you are interested in like this
path = request.fullpath[%r{^/(articles|comments)/}, 1] # articles or comments
Once you have it you can get the model class like that:
model_class = path.classify.constantize # Article or Comment Bests,
Richard
####Best Solution: Untilization of Routings
Brilliant, thanks. Further investigation showed that I can also do resources :comments, :controller => "contents", :type => "Comment" and then refer to params[:type]. But your solution also fits the bill and taught me classify and constantize. Thanks! – Sami Sep 3 '11 at 21:48
