Rails協會謎語：用戶，講師，學生和事件

Question

我用Google搜索，閱讀了文檔，並觀看了railscast，但是我無法用頭圍住它。 請幫忙。我在Ubuntu 13.04上運行最新的穩定Rai​​ls和Ruby 1.9.3。

我有一個User模型和一個Event模型。 現在，兩者之間有一個has_and_belongs_to_many關係。

然而，在現實生活中，User與Event有關，如Lecturer或Student。 A User既可以是Student也可以是Lecturer，但不適用於相同的事件。 Lecturer或Student尚未在我的應用程序模型，我不確定他們應該是單獨的模型。 我需要幫助來實現這個邏輯。

我想達到的目標是這樣的：

Event.first.lecturers＃應該返回此特定事件講師用戶。

Event.first.students＃應該返回此特定事件的學生用戶

User.first.events :as => :student＃應該返回活動爲特定的用戶，其中 用戶是學生

User.first.events :as => :lecturer＃應該返回活動針對特定用戶的地方 用戶是講師

我在想也許has_many :through協會可能工作，但我很困惑。 任何和所有指導讚賞。

問候，

納迪姆

Answer 1

您可以創建兩個連接表events_students和events_lecturers和設置模型這樣

class Event < ActiveRecord::Base 
    has_and_belongs_to_many :students, :class_name => 'User', :join_table => :events_students, :association_foreign_key => :user_id 
    has_and_belongs_to_many :lecturers, :class_name => 'User', :join_table => :events_lecturers, :association_foreign_key => :user_id 
end 

class User < ActiveRecord::Base 
    has_and_belongs_to_many :student_events, :class_name => 'Event', :join_table => :events_students, :association_foreign_key => :event_id 
    has_and_belongs_to_many :lecturer_events, :class_name => 'Event', :join_table => :events_lecturers, :association_foreign_key => :event_id 
end 

，然後訪問它：

Event.first.students 
Event.first.teachers 
User.first.student_events 
User.first.lecturer_events 

UPD。

另一種解決方案是使用的has_many：通過

class User < ActiveRecord::Base 
    has_many :event_assignments 
    has_many :student_events, :through => :event_assignments, :source => :event, :conditions => {'event_assignments.type' => 'EventAssignment::Student'} 
    has_many :lecturer_events, :through => :event_assignments, :source => :event, :conditions => {'event_assignments.type' => 'EventAssignment::Lecturer'} 
end 

class Event < ActiveRecord::Base 
    has_many :event_assignments 
    has_many :students, :through => :event_assignments, :source => :user, :conditions => {'event_assignments.type' => 'EventAssignment::Student'} 
    has_many :lecturers, :through => :event_assignments, :source => :user, :conditions => {'event_assignments.type' => 'EventAssignment::Lecturer'} 
end 

class EventAssignment < ActiveRecord::Base 
    belongs_to :user 
    belongs_to :event 
end 

class EventAssignment::Student < EventAssignment 
end 

class EventAssignment::Lecturer < EventAssignment 
end 

我使用STI爲EventAssignment模式，因爲如果你有不同的類型分配不同的邏輯也可以是有用的。但是，如果不需要它，只是用另一列名稱，而不是在type加入模型來識別關係類型：

class User < ActiveRecord::Base 
    has_many :event_assignments 
    has_many :student_events, :through => :event_assignments, :source => :event, :conditions => {'event_assignments.kind' => 'student'} 
    has_many :lecturer_events, :through => :event_assignments, :source => :event, :conditions => {'event_assignments.kind' => 'lecturer'} 
end 

class Event < ActiveRecord::Base 
    has_many :event_assignments 
    has_many :students, :through => :event_assignments, :source => :user, :conditions => {'event_assignments.kind' => 'student'} 
    has_many :lecturers, :through => :event_assignments, :source => :user, :conditions => {'event_assignments.kind' => 'lecturer'} 
end 

class EventAssignment < ActiveRecord::Base 
    belongs_to :user 
    belongs_to :event 
end