CODEWITHSUNDEEP
ruby-on-railsrubypostgresql
Tiamon
Tiamon

Reputation: 237

custom attributes in rails

I have a Student model and a method that does some calculations and returns a value

class Student < ActiveRecord::Base
  def total_result
     #some calculations
     return result
   end
end

Now in my students controller I would like to do the following

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

but this brings a PG::UndefinedColumn: ERROR. I am using postgres. How do I achieve this?

Upvotes: 1

Views: 562

Answers (1)

spickermann
spickermann

Reputation: 106832

You could use:

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

A word of warning: This will load all students from the database and calculate the value for each of them. This will be slow depending on the number of students in the table.

If you need this more frequently then it would make sense to store/cache the result of the calculation in the database.

Upvotes: 1

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