Rails 4 permit params DSL

permit_params_from.rb

def method_missing(symbol, *args, &block)
  p "Start method_missing from #{self} at #{symbol}"
  return unless symbol.to_s.start_with?('permit_params_from_')
  object = symbol.to_s.sub('permit_params_from_', '')
  context = []
  def context.method_missing(symbol, &block_b)
    p "Start context from #{self} at #{symbol}"
    second_context = []
    def second_context.method_missing(symbol)
      self << symbol
    end
    if block_given?
      second_context.instance_eval(&block_b)
      self << Hash[symbol, second_context]
    else
      self << symbol
    end

    p "Finish context from #{self} at #{symbol}"
  end
  context.instance_eval(&block)
  p "Finish from #{self} at #{symbol}"
  command = "params.require(#{object.to_sym}).permit(#{context})"
  p command
  puts context.inspect
end

permit_params_from_product_server do
  id
  name
  sku
  email do
    username
    server
  end
  home
  number
  serial_number
  image
end

Is not my best code, but my first DLS.

Output:

"Start method_missing from main at permit_params_from_product_server"
"Start method_missing from  at to_hash"
"Start context from [] at id"
"Finish context from [:id] at id"
"Start context from [:id] at name"
"Finish context from [:id, :name] at name"
"Start context from [:id, :name] at sku"
"Finish context from [:id, :name, :sku] at sku"
"Start context from [:id, :name, :sku] at email"
"Finish context from [:id, :name, :sku, {:email=>[:username, :server]}] at email"
"Start context from [:id, :name, :sku, {:email=>[:username, :server]}] at home"
"Finish context from [:id, :name, :sku, {:email=>[:username, :server]}, :home] at home"
"Start context from [:id, :name, :sku, {:email=>[:username, :server]}, :home] at number"
"Finish context from [:id, :name, :sku, {:email=>[:username, :server]}, :home, :number] at number"
"Start context from [:id, :name, :sku, {:email=>[:username, :server]}, :home, :number] at serial_number"
"Finish context from [:id, :name, :sku, {:email=>[:username, :server]}, :home, :number, :serial_number] at serial_number"
"Start context from [:id, :name, :sku, {:email=>[:username, :server]}, :home, :number, :serial_number] at image"
"Finish context from [:id, :name, :sku, {:email=>[:username, :server]}, :home, :number, :serial_number, :image] at image"
"Finish from main at permit_params_from_product_server"
"params.permit(product_server).require([:id, :name, :sku, {:email=>[:username, :server]}, :home, :number, :serial_number, :image])"
[:id, :name, :sku, {:email=>[:username, :server]}, :home, :number, :serial_number, :image]