Automatic bootstrap form validation on *_id fields when validates :association, presence: true is present

bootstrap_errors_for_associations.rb

BootstrapForm::FormBuilder.class_eval do
  def association_object(name)
    name = name.to_s

    if name.end_with?('_ids')
      # Check for a has_(and_belongs_to_)many association (these always use the _ids postfix field).
      association = object.class.reflect_on_association(name.chomp('_ids').pluralize.to_sym)
    else
      # Check for a belongs_to association with method_name matching the foreign key column
      association = object.class.reflect_on_all_associations.find do |a|
        a.macro == :belongs_to && a.foreign_key == name
      end
    end

    return association
  end

  alias_method :super_has_error?, :has_error?
  alias_method :super_get_error_messages, :get_error_messages

  def has_error?(name)
    association = association_object(name)
    if association.present?
      !object.errors[association.name].empty? || super_has_error?(name)
    else
      super_has_error?(name)
    end
  end

  def get_error_messages(name)
    assocation = association_object(name)
    if assocation.present?
      (object.errors[assocation.name] + super_get_error_messages(name).split(', ')).join(', ')
    else
      super_get_error_messages(name)
    end
  end
end