RoR定義兩個模型之間有意義的關系

Question

我想在Rails項目中定義多對多關系。 賦予個人關系不同含義的最佳方法是什么？

+------------+        has many        +-------------+
|            | ---------------------> |             |
|   person   |                        |   project   |
|            | <--------------------- |             |
+------------+        has many        +-------------+

這個模型對於一個開始是很好的，但是對於我想要實現的目標是不夠的。 一個人應該能夠在項目中扮演不同的角色。 例如，電影中有演員，制片人，特技演員，...

解決方案應該...

• 提供定義新關系類型（“角色”）的簡便方法
• 很好地集成到軌道中
• 盡可能快

最好的選擇是什么？

Answer 1

最好的方法是創建一個豐富的聯接表。

即：

       |  has many =>  |        |  <= has many  |
Person |               | Credit |               | Movie
       | <= belongs to |        | belongs to => |

與最初的示例相比，“人物”和“電影”沒有太大變化。 信用不僅包含person_id和movie_id，還包含更多字段。 信用的額外字段將是角色和角色。

然后，這只是一個具有許多直通關系的關系。 但是，我們可以添加額外的關聯以獲取更多詳細信息。 與電影示例保持一致：

class Person < ActiveRecord::Base
  has_many :credits
  has_many :movies, :through => :credits, :unique => true
  has_many :acting_credits, :class_name => "Credit",
    :condition => "role = 'Actor'"
  has_many :acting_projects, :class_name => "Movie",
    :through => :acting_credits
  has_many :writing_credits, :class_name => "Credit", 
    :condition => "role = 'Writer'"
  has_many :writing_projects, :class_name => "Movie",
    :through => :writing_credits

end 

class Credit < ActiveRecord::Base
  belongs_to :person
  belongs_to :movie
end

class Movie < ActiveRecord::Base
  has_many :credits
  has_many :people, :through => :credits, :unique => true
  has_many :acting_credits, :class_name => "Credit",
   :condition => "role = 'Actor'"
  has_many :actors, :class_name => "Person", :through => :acting_credits
  has_many :writing_credits, :class_name => "Credit", 
   :condition => "role = 'Writer'"
  has_many :writers, :class_name => "Person", :through => :writing_credits
end

與所有這些額外的關聯。 以下各項僅是一個SQL查詢：

@movie.actors  # => People who acted in @movie
@movie.writers # => People who wrote the script for @movie

@person.movies # => All Movies @person was involved with
@person.acting_projects # => All Movies that @person acted in

Answer 2

人員，項目和角色之間的關系應該是自己的表格。 制作一個具有一個人，一個項目以及該人在該項目中的角色的工作分配類。 然后Person has_many :projects, :through => :assignments 。