Render breadcrumbs in JSON-LD with Breadcrumbs On Rails

_json_ld_breadcrumbs.html.erb

<!-- app/views/layouts/_json_ld_breadcrumbs.html.erb -->
<script type="application/ld+json">
  <%= render_breadcrumbs builder: Breadcrumbs::JsonLdBuilder %>
</script>

json_ld_builder.rb

# app/lib/breadcrumbs/json_ld_builder.rb
class Breadcrumbs::JsonLdBuilder < BreadcrumbsOnRails::Breadcrumbs::Builder
  def render
    JSON.pretty_generate(
      "@context" => "http://schema.org",
      "@type" => "BreadcrumbList",
      "itemListElement" =>
        @elements.map.with_index(1) { |elt, idx| render_element(elt, idx) },
    )
  end

  private

  def render_element(element, index)
    {
      "@type" => "ListItem",
      "position" => index,
      "item" => {
        "@id" => "#{@context.root_url.chop}#{compute_path(element)}",
        "name" => compute_name(element),
      },
    }
  end
end

I have made a gem based on this Gist.
Please check necojackarc/breadcrumbs_on_rails-json_ld.