OrderAsSpecified adds the ability to query an ActiveRecord class for results from the database in an arbitrary order, without having to store anything extra in the database.

It's as easy as:

class TestObject
  extend OrderAsSpecified
end

TestObject.order_as_specified(language: ["es", "en", "fr"])
=> #<ActiveRecord::Relation [
     #<TestObject id: 3, language: "es">,
     #<TestObject id: 1, language: "en">,
     #<TestObject id: 4, language: "en">,
     #<TestObject id: 2, language: "fr">
   ]>

Other gems like ranked-model, acts_as_sortable, etc. assume you want the same ordering each time, and store data to keep track of this in the database. They're great at what they do, but if your desired ordering changes, or if you don't always want an ordering, this gem is your friend.

Add this line to your application's Gemfile:

gem 'order_as_specified'

And then execute:

$ bundle

Or install it yourself as:

$ gem install order_as_specified

Basic usage is simple:

class TestObject
  extend OrderAsSpecified
end

TestObject.order_as_specified(language: ["es", "en", "fr"])
=> #<ActiveRecord::Relation [
     #<TestObject id: 3, language: "es">,
     #<TestObject id: 1, language: "en">,
     #<TestObject id: 4, language: "en">,
     #<TestObject id: 2, language: "fr">
   ]>

This returns all TestObjects in the given language order. Note that this ordering is not possible with a simple ORDER BY. Magic!

Like any other ActiveRecord relation, it can be chained:

TestObject.
  where(language: ["es", "en", "fr"]).
  order_as_specified(language: ["es", "en", "fr"]).
  limit(3)
=> #<ActiveRecord::Relation [
     #<TestObject id: 3, language: "es">,
     #<TestObject id: 1, language: "en">,
     #<TestObject id: 4, language: "en">
   ]>

We can also use this when we want to sort by an attribute in another model:

TestObject.
  joins(:other_object).
  order_as_specified(other_objects: { id: [other1.id, other3.id, other2.id] })

Neat, huh?

In all cases, results with attribute values not in the given list will be sorted as though the attribute is NULL in a typical ORDER BY:

TestObject.order_as_specified(language: ["fr", "es"])
=> #<ActiveRecord::Relation [
     #<TestObject id: 2, language: "fr">,
     #<TestObject id: 3, language: "es">,
     #<TestObject id: 1, language: "en">,
     #<TestObject id: 4, language: "en">
   ]>

In databases that support it (such as PostgreSQL), you can also use an option to add a DISTINCT ON to your query when you would otherwise have duplicates:

TestObject.order_as_specified(distinct_on: true, language: ["fr", "en"])
=> #<ActiveRecord::Relation [
     #<TestObject id: 2, language: "fr">,
     #<TestObject id: 3, language: "en">,
     #<TestObject id: 4, language: "es">
   ]>

Note that if a nil value is passed in the ordering an error is raised, because databases do not have good or consistent support for ordering with NULL values in an arbitrary order, so we don't permit this behavior instead of allowing an unexpected result.

We have documentation on RubyDoc.

1. Fork it (https://github.com/panorama-ed/order_as_specified/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Make sure your changes have appropriate tests (bundle exec rspec) and conform to the Rubocop style specified. We use overcommit to enforce good code.

OrderAsSpecified is released under the MIT License.