copy child records from a duplicate activerecord object to another

gistfile1.txt

class ActiveRecord::Base
  def combine duplicate, update=false
    Rails.logger.info "Combine #{duplicate.name} child records into #{name}..."
    tbl = self.class.table_name
    self.class.has_many_associations.each do |relation, refl|
      assoc = ActiveRecord::Associations::HasManyAssociation.new(duplicate,refl)
      scope = assoc.scope
      cnt = scope.size
      any = cnt > 0
      Rails.logger.info "#{'combine ' if any}#{cnt} #{relation.singularize.pluralize(cnt)}"
      if any
        fk = refl.foreign_key
        val =  self.send(refl.active_record_primary_key)
        val = assoc.klass.connection.quote(val) if val.class==String
        update_value = "`#{fk}` = #{val}"
        if val
          if update
            scope.update_all(update_value)
          else
            Rails.logger.info "SET #{update_value}"
          end
        else
          Rails.logger.error "Error: no foreign_key (#{refl.active_record_primary_key}) value for the parent: #{self.name}"
        end
      end
    end
    self
  end

  def self.has_many_associations
    reflections.select{|ref,klazz|klazz.is_a? ActiveRecord::Reflection::HasManyReflection}
  end
end