重构ActiveRecord模型有一个基类与基本模块 [英] Refactoring ActiveRecord models with a base class versus a base module

问题描述

A类和B是相同的：

class A < ActiveRecord::Base
 def foo
  puts "foo"
 end
end

class B < ActiveRecord::Base
 def foo
  puts "foo"
 end
end

什么是重构之间的区别是这样一个基类

class Base < ActiveRecord::Base
 def foo
  puts "foo"
 end
end

class A < Base
end

class B < Base
end

与像这样使用基本模块

module Base
 def foo
  puts "foo"
 end
end

class A < ActiveRecord::Base
 include Base
end

class B < ActiveRecord::Base
 include Base
end

是一种方式preferable对另一？

推荐答案

还有其他所有的答案都缺少这两种方法之间的根本区别，那就是Rails的实施性传播感染的（单表继承）：

There's a fundamental difference between those two methods that all the other answers are missing, and that's rails' implementation of STIs (Single Table Inheritance):

<一个href="http://api.rubyonrails.org/classes/ActiveRecord/Base.html">http://api.rubyonrails.org/classes/ActiveRecord/Base.html （找到单表继承一节）

http://api.rubyonrails.org/classes/ActiveRecord/Base.html (Find the "Single Table Inheritance" section)

基本上，如果你重构你的基类是这样的：

Basically, if you refactor your Base class like this:

class Base < ActiveRecord::Base
  def foo
    puts "foo"
  end
end

class A < Base
end

class B < Base
end

那么，你应该有一个名为基地一个数据库表中，有一个名为类型一栏，里面应该有A或B的值。该表中的列将在所有的车型一样，如果你有一个只属于一个模型的一列，你的基地表将非规范化。

Then, you are supposed to have a database table called "bases", with a column called "type", which should have a value of "A" or "B". The columns on this table will be the same across all your models, and if you have a column that belongs to only one of the models, your "bases" table will be denormalized.

然而，如果你重构你的基类是这样的：

Whereas, if you refactor your Base class like this:

Module Base
  def foo
  puts "foo"
 end
end

class A < ActiveRecord::Base
 include Base
end

class B < ActiveRecord::Base
 include Base
end

然后就没有表基地。相反，会出现一个表作为和表BS。如果它们具有相同的属性，该列将在这两个表中复制，但如果有差异，他们不会被denomarlized

Then there will be no table "bases". Instead, there will be a table "as" and a table "bs". If they have the same attributes, the columns will have to be duplicated across both tables, but if there are differences, they won't be denomarlized.

因此​​，如果一个是preferable比其他，是的，但这是特定于应用程序。作为一个经验法则，如果他们有相同的属性或一个大的重叠，使用STI（第一例子），否则，使用模块（第二个示例）。

So, if one is preferable over the other, yes, but that's specific to your application. As a rule of thumb, if they have the exact same properties or a big overlap, use STI (1st example), else, use Modules (2nd example).

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