How to get rails to return SUM(columnName) attributes with right datatype instead of a string?

Question

Assume a query of the following form

operatingExpenses = Expense.find(:all,
      {:select=>\"categories.activityType, categories.name heading, sum(amount         


        

Answer 1

Active record is trying to return "Expense" objects built from the results of your query. But expense objects don't have a totalAmount field, so this is unrequested "bonus data" as far as ActiveRecord can tell. It coud just throw it out, but instead it keeps it for you, with the most forgiving type assumptions it can.

My suggestions:

• Don't do this; it isn't the way Active record is supposed to work; the total of the details belongs to whatever is rolling them up; it isn't a detail object itself.
• If you must treat it as a detail, name the field amount so ActiveRecord knows what to do with it.

• If you must have the total as its own field, add an accessor in your Expense model like so:

  def total_amount
      totalAmount.to_f
      end
  

  and use it like so: operatingExpenses[1].total_amount in your code.