gistfile1.txt

dynamic!(:my_security_group, :nat, {
  :description => 'My Shiny Security Group',
  :ingress => [
    {
      :cidr_ip => '0.0.0.0/0',
      :ip_protocol => 'icmp',
      :from_port => -1,
      :to_port => -1
    }
  ]
} 

gistfile2.txt

SparkleFormation.dynamic(:my_security_group) do |_name, _config = {}|
  resources("#{_name}_security_group".to_sym) do
    type 'AWS::EC2::SecurityGroup'

    ::SparkleFormation::SparkleStruct.camel_keys = true
    [ :ingress, :egress ].each do |dir|
      next unless _config[dir]
      _config[dir] = _config[dir].map { |rule| ::SparkleFormation::SparkleStruct.new(rule) }
    end

    properties do
      vpc_id _config[:vpc_id] || ref!(:vpc)
      group_description _config[:description]

      security_group_ingress _config[:ingress]
      security_group_egress _config[:egress]
    end
  end
end 

my_security_group.rb

SparkleFormation.dynamic(:my_security_group) do |_name, _config = {}|
  resources("#{_name}_security_group".to_sym) do
    type 'AWS::EC2::SecurityGroup'

    properties do
      vpc_id _config[:vpc_id] || ref!(:vpc)
      group_description _config[:description]

      security_group_ingress _config[:ingress]
      security_group_egress _config[:egress]
    end
  end
end