where_or.rb

module WhereOr

  def where_or(*scopes)
    conditions = scopes.inject(self) { |scoped, scope| scoped.send(scope) }
    conditions = conditions.where_values.map { |where_value| where_value.respond_to?(:to_sql) ? where_value.to_sql : where_value }
    conditions = conditions.join(" OR ")
    where(conditions)
  end

  ActiveRecord::Base.send :extend, self

end

class Person < ActiveRecord::Base

  scope :teenager,  where("age >= 12 AND age <= 18")
  scope :married,   where(:married => true)

end

Person.where_or(:teenager, :married) # => "SELECT "people".* FROM "people" WHERE (age >= 12 AND age <= 18 OR "people"."married" = 't')"