Enhanced error reporting for complex forms

Ryan Bates has a great series of RailsCasts about complex forms, in which multiple models are on one form. The problem is, errors are not easy to report and identify. But a clever viewer of the casts came up with a great solution which I took a little further.

The problem with the enhancement by ChrisFF was that the error message was including the top-level models "Invalid #{child}" message, which is totally useless once you have the actual error message for the child. So I added a bit of code to delete the top-level model error:

[UPDATE: June 24, 2008]
I've updated this code to cull out repeating association errors. Old code is at bottom of this post.

## add to model (can be in protected section)
def after_validation()
  return if errors.empty?
  associations_harvested = []
  associations = self.class.reflect_on_all_associations.collect(&:name)
  errors.each do |field, useless_message|
    next unless associations.index(field.to_sym) && !associations_harvested.include?(field)
    associations_harvested << field
    Array(send(field.to_sym)).each do |assoc_object|
      next if assoc_object.valid?
      assoc_object.errors.each_full do |useful_message|
        errors.add_to_base "#{assoc_object.class.name}: #{useful_message}"
      end
    end
    # calls our ActiveRecord::Errors#delete monkey patch to get rid of useless message
    errors.delete field
  end
end


## add to config/initializers/monkey_patches.rb
class ActiveRecord::Errors
  def delete(attribute)
    @errors.delete attribute.to_s
  end
end

(This could be packaged as a slimline plugin.)

I also used recipe #30 from the Advanced Rails Recipes book, "Keep Forms DRY and Flexible" to create an errors handling form that rocks. Using CSS, I have a form that can highlight the error field and provides a nice error message right next to the field. Very nice looking.


[UPDATE: June 24, 2008]
I've updated the above code to cull out repeating association errors. For reference, here is the old code -- DO NOT USE THIS CODE!

  NOTE: DO NOT USE THIS CODE!
  def after_validation
    return if errors.empty?
    # Get an array of associations
    associations = self.class.reflect_on_all_associations.collect(&:name)
    # Iterate through the errors
    errors.each do |field,message|
      # If the field of an error is really an association, then the 'validates_associated' found an error
      next unless associations.index(field.to_sym)
      # Iterate through the objects in the association looking for the invalid ones
      [self.send(field)].flatten.each do |association|
        if association and !association.valid?
          # add the error messages of the associated object to my error messages
          association.errors.each_full do |msg|
            self.errors.add_to_base "#{association.class.name}: #{msg}"
          end
        end
        errors.delete field
      end
    end
  end