根据其他资源删除资源

Question

--我有用户和项目资源，以及连接他们的连接表，称为project_members。当所有用户离开项目时，项目都会自毁，比如下面的规范：

 75     it 'deletes the project when there are no more users on it' do
 76       lambda do
 77         project.users.clear 
 78       end.should change(Project, :count).by(-1)
 79     end

到目前为止，我想出了这句话，但不知道该放在哪里.

@project.destroy if @project.users.empty?

编辑:这是我的模特

用户模型(我正在使用设计)

  1 class User < ActiveRecord::Base
  2 
  3   has_many :synapses #aka project_members      
  4   has_many :projects, :through => :synapses
  5 
  6   # Include default devise modules. Others available are:
  7   # :token_authenticatable, :encryptable, :lockable, :timeoutable and :omniauthable
  8   devise :database_authenticatable, :registerable,
  9          :recoverable, :rememberable, :trackable, :validatable,
 10          :confirmable      
 11   
 12   # Setup accessible (or protected) attributes for your model
 13   attr_accessible :email, :password, :password_confirmation, :remember_me
 14 end

项目模型

  1 class Project < ActiveRecord::Base
  2 
  3   has_many :synapses
  4   has_many :users, :through => :synapses, :dependent => :nullify
  5   has_many :tasks, :dependent => :destroy
  6 
  7   #use this when you don't have callbacks
  8   #has_many :tasks, :dependent => :delete_all
  9 
 10   validates :name, :presence => true,
 11             :uniqueness => true
 12   validates :description, :presence => true
 13 
 14   attr_accessible :name, :description
 15 
 16 end

突触模型(项目成员)

  1 class Synapse < ActiveRecord::Base
  2 
  3   belongs_to  :user,
  4               :class_name => 'User',          
  5               :foreign_key => 'user_id'       
  6   belongs_to  :project,
  7               :class_name => 'Project',       
  8               :foreign_key => 'project_id'    
  9   
 10 end

任务模型

  1 class Task < ActiveRecord::Base
  2 
  3   belongs_to :project
  4   belongs_to :user
  5 
  6   validates :name, :presence => true
  7   validates :description, :presence => true,
  8                           :length => { :minimum => 10 }
  9 
 10   attr_accessible :name, :description
 11 
 12 end

Answer 1

成员资格模型的回调应该做到这一点：

class ProjectMember < ActiveRecord::Base
  after_destroy :remove_project_if_last_member
  private
    def remove_project_if_last_member
      project.destroy if project.users.empty?
    end
end

Answer 2

首先，您的关系语句可以简化：

belongs_to  :user,
  :class_name => 'User',          
  :foreign_key => 'user_id'

会变得很简单

belongs_to  :user

:class_name和:foreign_key属性是默认的，因为您已经拥有了它们。

如果最后一个用户离开了该项目，您应该在Synapses类上添加一个回调，以破坏它。就像这样：

class Synapse < ActiveRecord::Base

  after_destroy :remove_project_if_last_member

  private

  def remove_project_if_last_member
    project.destroy if project.users.empty?
  end

end

注意:我从另一个答案中复制了after_destroy回调--如果那个已经很好的话，就没有意义编造一些东西。