>> @shop.items 
=> [Item id:21 shop_id: 1, Item id: 22, shop_id: 1, ....]
>> @shop.item.find_all_by_category("CPU") 
=> [Item id:23 shop_id: 1, Item id: 26, shop_id: 1, ....]

>> @shop.items.delete_all

  Item UPDATE (3.0ms)   UPDATE `items` SET shop_id = NULL WHERE (shop_id = 1 AND id IN (22,23,24,25,26))

# File vendor/rails/activerecord/lib/active_record/base.rb, line 897
897:       def delete_all(conditions = nil)
898:         sql = "DELETE FROM #{quoted_table_name} "
899:         add_conditions!(sql, conditions, scope(:find))
900:         connection.delete(sql, "#{name} Delete all")
901:       end

>> @shop.items.destroy_all

Item Destroy (3.0ms)   DELETE FROM `items` WHERE WHERE id = 21
Item Destroy (3.0ms)   DELETE FROM `items` WHERE WHERE id = 22
Item Destroy (3.0ms)   DELETE FROM `items` WHERE WHERE id = 23

def create
  if @user = User.create(params[:user])
    flash[:notice] = 'ユーザ作成しました'
    redirect_to :action => 'index'
  else
    # ここでは、@user.errors でエラーが取れる
    render :action => 'new'
  end
end

def create
  @user = User.create!(params[:user])
  flash[:notice] = 'ユーザ作成しました'
  redirect_to :action => 'index'
rescue ActiveRecord::RecordInvalid => e
  # @user は nil になっているので、 @user.errors でエラーが取れない。
  render :action => 'new'
end

def create
  @user = User.create!(params[:user])
  flash[:notice] = 'ユーザ作成しました'
  redirect_to :action => 'index'
rescue ActiveRecord::RecordInvalid => e
  # e.record に Userクラスのインスタンスが入ってる。
  @user = e.record
  render :action => 'new'
end

< %= error_messages_for :user %>

# TODO 退会のフローについてメール確認待ち 090420

% rake notes
app/models/user.rb:
  * [267] [TODO] 退会のフローについてメール確認待ち 090420

% rake --tasks
rake notes                           # Enumerate all annotations
rake notes:fixme                     # Enumerate all FIXME annotations
rake notes:optimize                  # Enumerate all OPTIMIZE annotations
rake notes:todo                      # Enumerate all TODO annotations

% sudo gem so -a http://gems.github.com
% sudo gem i amatsuda-i18n_generators

% ./script/generate i18n ja

% vi config/locales/active_record_ja.yml

ja:
  activerecord:
    models:
      user: 'ユーザ'
    attributes:
      user:
        name: '名前'
        email: 'メールアドレス'
....