缺少属性错误 Rails

Question

当我收到此错误消息时，我似乎无法在视图中显示范围的结果。我正在尝试将当天的所有会员数量加起来并显示为总数

missing attribute: membership_id

我的模型和范围

class Member < ActiveRecord::Base
 belongs_to :membership
 accepts_nested_attributes_for :membership

 attr_accessible :membership_id, :forename, :middlename, :surname, :house_no, :house_name, :street, :town, :postcode, :home_tel, :mobile_tel, :work_tel, :email, :start_date, :expiry_date

scope :new_memberships_cash_today, ->() {
joins(:membership).where(:start_date => Date.today).select('ROUND(SUM(memberships.cost), 2)')
}
end

class Membership < ActiveRecord::Base
has_many :members, :dependent => :destroy
attr_accessible :membership_type, :cost 
end

然后是我的观点

columns do

  #Total amount in £ for New Memberships today
   column do
    panel "Cash Today", :class => 'NewAmountMemberships' do
     table_for Member.new_memberships_cash_today  do 
      column 'Total cash' do |c|
       c.membership.map { |e| [e.cost, e.id] }
      end 
     end     
    end
   end
  end

经过一番阅读，似乎我的 select 调用在范围内可能存在问题，因为我需要指定所有模型属性才能使用 Active Record 成功调用？

当我在选择中执行求和时，我不确定如何添加更多属性，如果是这样的话

任何帮助表示赞赏

我已经在控制台中运行了范围，这就是返回的内容

Member Load (0.1ms)  SELECT ROUND(SUM(memberships.cost), 2) FROM `members` INNER JOIN `memberships` ON `memberships`.`id` = `members`.`membership_id` WHERE `members`.`start_date` = '2013-12-13'
=> #<ActiveRecord::Relation [#<Member id: nil>]>

Answer 1

我不会在作用域中执行此操作，而是在辅助方法中执行此操作。这样您就可以获取相关记录并调用您的方法来返回总数。

类似这样的事情：

def membership_sum(memberships = [])
  sum = 0
  memberships.each { |membership| sum += membership.cost }
  sum.round
end

现在，将关联的记录存储在@memberships 变量中（从您的控制器中），然后在您的视图中使用<%= membership_sum(@memberships) %>