API Response Serialization with Plain Old Ruby Objects and ActiveSupport

If you are building an API application with Ruby on Rails, you will notice that the jbuilder gem is suggested in the default Gemfile. Jbuilder allows you to create JSON using a builder domain specific language. Some people prefer ActiveModel::Serializers which has its own DSL, is more declarative and handles structural conventions for you. This is convenient if you want your API to conform to the JSON API specification or a custom format.

While these gems (and others) each have their trade-offs, in some projects, they are more of a hindrance than help. I have another serialization strategy for these cases.

The Ruby standard library supports encoding primitives to JSON and ActiveSupport adds a layer on top of that to allow serialization of any Ruby object by first serializing it to a Hash. In my code, I build a hash directly:

class PostSerializer
  def initialize(post)
    @post = post
  end

  def serialize
    {
      title: post.title,
      author: post.author
    }
  end

  private

  attr_reader :post
end

Then in a controller, I would have something like:

def show
  post = Post.find(params[:id])
  render json: PostSerializer.new(post).serialize.to_json
end