Mark Needham

I managed to create an interesting problem for myself while playing around with some code whereby I was ending up with validation errors appearing twice every time I called ‘valid?’ on a specific model.

I figured I was probably doing something stupid and in fact a few replies by Aaron Baldwin on a mailing list thread on ‘rubyonrails-talk’ helped explain exactly what I’d done:

Are you calling require ‘employee’ anywhere? If so you are likely
causing the model to load twice which causes duplicate errors because
the validates_presence_of method gets called twice.

I’d put the following code into a controller elsewhere somewhat unnecessarily since it didn’t seem to be picking up the location of my model at the time:

code_submissions_controller.rb

require 'models/code_submission'
 
class CodeSubmissionsController < ApplicationController
  def new
    CodeSubmission.new  
  end
end

require doesn’t load a file if it’s already been included but Aaron points out why it does on this occasion:

You are right that “require” will only load the file once. But if you load the class another way calling “require” will load it again.

As I understand it that controller code would also implicitly require ‘code_submission’ by the convention of inserting an underscore between the ‘CodeSubmission’ constant’s names.

We therefore effectively have the following two requires:

require 'code_submission'
require 'models/code_submission'

Which explain how the file gets loaded twice and therefore why the validation method fires twice and therefore creates two errors!