最好的方法，通過一個多態關聯

Question

所以排序 - 具有以下設置：

class Event < ActiveRecord::Base 
has_many :invitations 
end 

class Invitation < ActiveRecord::Base 
    belongs_to :guest, :polymorphic => true 
    belongs_to :event 
end 

class Member > ActiveRecord::Base 
    has_many :invitations, :as => :guest 

    def full_name 
    [first_name, last_name].join(" ") 
    end 
end 

class Visitor > ActiveRecord::Base 
    has_many :invitations, :as => :guest 

    def full_name 
    name 
    end 
end 

最後，我希望能夠獲取由客人訂購了活動邀請FULL_NAME。我無法弄清楚 - 誰能幫我解決這個問題？將不勝感激:)

Answer 1

至於full_name是一個虛擬的屬性，我可以想像，只有紅寶石的解決方案，不是SQL

event = Event.find some event 
event.invitations.sort_by(&:full_name)