鐵路cancancan深has_many通過

Question

我有一個問題，同時定義用戶和ClassD之間的關聯深入的能力。

User < ActiveRecord::Base 
    has_many :classB 
    has_many :classC, through classB 
    has_many :classD, through classB 
end 
ClassB < ActiveRecord::Base 
    belongs_to :User 
    has_many :classC 
    has_many :classD, through classC 
end 
ClassC < ActiveRecord::Base 
    belongs_to ClassC 
    has_many :ClassD 
end 
ClassD < ACtiveRecord::Base 
    belongs_to Class C 
end 

我如何定義的能力與cancancan，是這樣的：

class Ability 
    include CanCan::Ability 

    def initialize(user) 
    user ||= User.new  
    can :manage, ClassD do |cd| 
     cd.user_id: user.id 
    end 

    end 
end 

Answer 1

class Ability 
    include CanCan::Ability 

    def initialize(user) 
    user ||= User.new  
    can :manage, ClassD do |cd| 
     user.cds.exists?(cd.id) 
    end 

    end 
end