Question

我有用户和项目资源以及连接它们的连接表名为project_members。我希望在所有用户离开项目时都有功能，项目会自行销毁，如下所示：

 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，我想出了这条线，但不知道该把它放在哪里......

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

编辑：这是我的模特

用户模型（我正在使用Devise）

  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

Synapses model AKA（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

会员模型的回调应该这样做：

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，您的关系陈述可以简化：

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

可以简单地

belongs_to  :user

无论如何，:class_name和:foreign_key属性都是默认属性。

如果最后一个用户离开，你应该在Synapses类上放置一个回调来销毁Project。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：我从另一个答案复制了after_destroy回调 - 如果那个已经很好的话就没有意义。]

根据其他资源删除资源

2 个答案: