make attachments accesible from user model and fix cleaning up attachment on destroy

app/models/attachment.rb

@@ -7,4 +7,14 @@ class Attachment < ActiveRecord::Base
 
   do_not_validate_attachment_file_type :file
   # validates_attachment_content_type :file, :content_type => ["text/plain"]
+
+  before_destroy :delete_attached_file
+
+  private
+
+  def delete_attached_file
+    file = nil
+    save!
+  end
+
 end

app/models/todo.rb

@@ -25,7 +25,7 @@ class Todo < ActiveRecord::Base
   has_many :pending_successors, -> {where('todos.state = ?', 'pending')}, :through => :predecessor_dependencies,
     :source => :successor
 
-  has_many :attachments, dependent: :delete_all
+  has_many :attachments, dependent: :destroy
 
   # scopes for states of this todo
   scope :active, -> { where state: 'active' }

app/models/user.rb

@@ -96,6 +96,7 @@ class User < ActiveRecord::Base
 
   has_many :notes, -> { order "created_at DESC" }, dependent: :delete_all
   has_one :preference, dependent: :destroy
+  has_many :attachments, through: :todos
 
   validates_presence_of :login
   validates_presence_of :password, if: :password_required?