扶手：我如何模型$ P ​​$ pferences？我应该使用的has_many：通过？ [英] Rails: How do I model preferences? Should I use has_many :through?

问题描述

我有两个模式：用户和染发。用户只有一根头发的颜色，但可以有许多头发的颜色preferences。什么是这个模型的最佳方法是什么？

I have two models: User and HairColor. A user has only one hair color, but can have many hair color preferences. What's the best way to model this?

这就是我开始做的：

#models/user.rb
class User < ActiveRecord::Base
  belongs_to :hair_color
  has_many :preferences, 
  has_many :hair_colors, :through => :preferences
end

#models/hair_color.rb
class HairColor < ActiveRecord::Base 
  has_many :users
end

#models/preference.rb
class Preference < ActiveRecord::Base 
  belongs_to :user
  belongs_to :hair_color
end

时使用的has_many：通过正确的方法？另外，如果我想要的这个扩展到其他属性，如睛彩？ （A用户有一个眼睛的颜色，但可以preFER许多眼睛的颜色

Is using has_many :through the right approach? Also what if I want to extend this to other attributes such as "eye color"? (A user has one eye color, but can prefer many eye colors"

推荐答案

有将发色数量有限，所以preference表需要有一个 hair_color_id 键，设置像这样：

There will be a limited amount of hair colors, so the preference table needs to have a hair_color_id and be set up like so:

#models/user.rb
class User < ActiveRecord::Base
  has_one :hair_color
  has_many :preferences
end

#models/hair_color.rb
class HairColor < ActiveRecord::Base 
  belongs_to :user
  belongs_to :preference
end

#models/preference.rb
class Preference < ActiveRecord::Base 
  belongs_to :user
  has_many :hair_color
end

我相信这是正确的。让我知道如果您遇到任何障碍。

I believe that's correct. Let me know if you run into any snags.

当您添加眼睛的颜色或任何其他特征，你可能必须做一些与preference不同。我有4列在这一点上：的id，USER_ID，foreign_id，foreign_type

When you add eye color or any other characteristic, you'll probably have to do something different with preference. I'd have 4 columns at that point: id, user_id, foreign_id, foreign_type

foreign_id会从eye_color / hair_color表中的ID，并foreign_type将是眼睛或毛什么的。然后，在你的模型，你有这样的事情：

foreign_id would be the id from the eye_color/hair_color table, and foreign_type would be "eye" or "hair" or something. Then in your model, you'd have something like this:

#models/hair_color.rb
class HairColor < ActiveRecord::Base 
  belongs_to :user
  has_many :preferences, :foreign_key => :foreign_id, :conditions => { "preferences.foreign_type" => "hair" }
end

这变得有点疯狂，但它是这样做的最干的方法。你会把同样的事情在你的eye_color.rb，只是替换毛与眼睛为foreign_type。

That gets a little crazy, but it's the most DRY way of doing it. You'd put the same thing in your eye_color.rb and just replace "hair" with "eye" for the foreign_type.

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