ruby - custom attributes in rails -

i have student model , method calculations , returns value

class student < activerecord::base   def total_result      #some calculations      return result    end end

now in students controller following

student.where("total_result > ?", params[:result])

but brings pg::undefinedcolumn: error. using postgres. how achieve this?

you use:

student.select { |student| student.total_result > params[:result] }

a word of warning: load students database , calculate value each of them. slow depending on number of students in table.

if need more make sense store/cache result of calculation in database.

Jal