Boxer is a template engine for creating nested and multi-view JSON objects from Ruby hashes.

Say you have a couple ActiveRecord models in your Rails app and you want to render an API response in JSON, but the view of each of those model objects may change based on the API action that's being requested.

• User
• Place

For instance, the API for GET /users/:id should render a full representation of the User object in question, including all relevant attributes.

But in your GET /places/:id/users API call, you only need short-form representations of the users at that place, without every single attribute being included in the response.

Boxer allows you to define a box for each type of object you'd like to display (or for each amalgamation of objects you want to display—it's up to you).

Boxer.box(:user) do |box, user|
  {
    :name => user.name,
    :age  => user.age,
  }
end

To display different views on the same object, you can use Boxer's views:

Boxer.box(:user) do |box, user|
  box.view(:base) do
    {
      :name => user.name,
      :age  => user.age,
    }
  end

  box.view(:full, :extends => :base) do
    {
      :email      => user.email,
      :is_private => user.private?,
    }
  end
end

As you might guess, the :full view includes all attributes in the :base view by virtue of the :extends option.

Now, in order to render a User with the :base view, simple call Boxer.ship:

Boxer.ship(:user, User.first)

Boxer assumes that you want the :base view if no view is specified to ship—it's the only specially-named view.

To render the full view for the same user:

Boxer.ship(:user, User.first, :view => :full)

Which will give you back a Ruby hash on which you can call #to_json, to render your JSON response¹:

>> Boxer.ship(:user, User.first, :view => :full).to_json
=> "{"name": "Bo Jim", "age": 17, "email": "[email protected]", "is_private": false}"

Composing different boxes together is as simple as calling Boxer.ship from within a box—it's just Ruby:

Boxer.box(:place) do |box, place|
  {
    :name     => place.name,
    :address  => place.address,
    :top_user => Boxer.ship(:user, place.users.order(:visits).first),
  }
end

1. Hash#to_json requires a json library

See the wiki for more features of Boxer, including:

• Extra Arguments
• Preconditions
• Helper Methods in Boxes
• Box Includes
• Multiple Inheritance

Install the boxer gem.

• Brad Fults, Gowalla Incorporated

Boxer was inspired by RABL, by Nathan Esquenazi.