app/models/shelf.rb in enju_library-0.1.0.pre39 vs app/models/shelf.rb in enju_library-0.1.0.pre40

@@ -1,17 +1,17 @@
 class Shelf < ActiveRecord::Base
-  attr_accessible :name, :display_name, :note, :library_id, :closed
   include MasterModel
   scope :real, -> { where('library_id != 1') }
   belongs_to :library, validate: true
   has_many :items
   has_many :picture_files, as: :picture_attachable, dependent: :destroy
 
   validates_associated :library
   validates :library, presence: true
   validates_uniqueness_of :display_name, scope: :library_id
   validates :name, format: { with: /\A[a-z][0-9a-z\-_]{1,253}[0-9a-z]\Z/ }
+  before_update :reset_position
 
   acts_as_list scope: :library
 
   searchable do
     string :name
@@ -33,17 +33,18 @@
 
   def self.web
     Shelf.find(1)
   end
 
-  def first?
-    # 必ずposition順に並んでいる
-    return true if library.shelves.first.position == position
-    false
-  end
-
   def localized_display_name
     display_name.localize
+  end
+
+  # http://stackoverflow.com/a/12437606
+  def reset_position
+    if library_id_changed?
+      self.position = library.shelves.count > 0 ? library.shelves.last.position + 1 : 1
+    end
   end
 end
 
 # == Schema Information
 #