Question

I have this class and these methods inside of it.

class Purchase < ActiveRecord::Base
  belongs_to :user
  belongs_to :price
  belongs_to :unit_price

  scope :today, lambda { joins(:unit_price, :price).
                       where(:prices => { :date => Date.today }, 
                       :unit_prices =>  { :date => Date.today } ) }

  # not working                                 
  def total
    self.price.sum(:amount) + self.unit_price.sum(:amount)
  end
end

When I try to use my scope chain like this:

<%= current_user.purchases.today.map(&:total) %>

It gives me an empty Array result of []. I’m really trying to do this.

<%= number_to_currency(current_user.purchases.today.map(&:total)) %>

But this doesn’t work either for this error occurs.

undefined method `to_f' for []:Array

Why does it come back empty?

Thanks.

Answer 1

Your today scope must be reducing the resultset to zero results. That is, if current_user has any purchases in the first place. Are you sure a Price‘s date is actually a Date? Are you sure the :prices association exists on Purchase (although I guess it would probably throw a NoMethodError there if it didn’t)?

As for your undefined method to_f for []:Array, even if you weren’t working with an empty array, you’d still be trying to cast your array as a float. You’ll want to sum the array of prices you’ll get, and pass that to number_to_currency:

number_to_currency(current_user.purchases.today.map(&:total).sum)