Array of Hashes input for ActiveAdmin and Formtastic

active_admin.js

$('.array-of-hashes-tables').on('click', '.array-of-hashes-table .remove', function(event) {
  event.preventDefault();
  $(this).closest('.array-of-hashes-table').remove();
});

$('.array_of_hashes .add').on('click', function(event) {
  event.preventDefault();
  var $this = $(this);
  var $tables = $this.siblings('.array-of-hashes-tables');
  var $cloneable = $tables.find('.cloneable').first();
  var $clone = $cloneable.clone();
  $tables.append($clone);
  $clone.find('input').removeAttr('disabled');
  $clone.removeClass('cloneable');
  $clone.show();
});

array_of_hashes_input.rb

class ArrayOfHashesInput
  include Formtastic::Inputs::Base
  include ActionView::Helpers::FormTagHelper

  def to_html
    array_html = []

    first_object = {}
    options[:with_keys].each do |key|
      first_object[key] = ""
    end

    array_html << input_wrapping do
      hash_html = []
      hash_html << '<div class="array-of-hashes-tables">'

      ([first_object] + Array.wrap(object.send(method))).each_with_index do |hash, index|
        hash_html << '<table class="array-of-hashes-table'
        hash_html << ' cloneable' if index == 0
        hash_html << '"'
        hash_html << ' style="display: none;"' if index == 0
        hash_html << '><tbody><tr>'

        hash = eval(hash) unless hash.is_a?(Hash)
        hash.each do |key, value|
          tag = text_field_tag("site_config[#{method}][][#{key}]", value, disabled: index == 0 ? true : nil)
          hash_html << "<td>#{tag}</td>"
        end

        hash_html << '<td><a href="#" class="button remove">Remove</a></td>'
        hash_html << "</tr></tbody></table>"
      end

      hash_html << "</div>"

      hash_html << '<a href="#" class="button add">Add</a>'
      hash_html.join("").html_safe
    end

    array_html.join("\n").html_safe
  end
end

Could you include an example of how to use this?