Accessing Model ID inside of rails form helper - ruby-on-rails

Question

First off I'm new to rails, I have a join table Menus_orders which I'm trying to load ID's into on create.
I have this form helper which has access to Order.new(:id, :name) fields and fields_for Menus_order(:menu_id, :order_id). I can insert the menu_id from a select but I can't for the life of me figure out how to populate a hidden input with the current order_id which the form holds in #order.
look at ORDER_ID HERE
<div class="form">
<h1>Create a new order</h1>
<%= form_for #order do |f| %>
<%= f.label :name%><br>
<%= f.text_field :name%><br>
<h3>Select meals</h3>
<%= fields_for(#menus_order) do |i| %>
<div class="field">
<%= i.select :menu_id, options_for_select(Menu.all.pluck(:id)) %>
<%= i.hidden_field :order_id, :value => ORDER_ID HERE %>
</div>
<% end %>
<br>
<%= f.submit "Create"%><br>
<% end %>
</div>
Thanks, DW

Answer 1

You should use nested attributes for order model just apply
the conventions right & it will be handled, you can achieve this by
following example :
order.rb should be like :
class Order < ActiveRecord::Base
has_many :menu_orders
accepts_nested_attributes_for :menu_orders
end
menu_order.rb be like :
class MenuOrder < ActiveRecord::Base
belongs_to :order
end
orders/new.html
<div class="form">
<h1>Create a new order</h1>
<%= form_for #order do |f| %>
<%= f.label :name%><br>
<%= f.text_field :name%><br>
<h3>Select meals</h3>
<%= f.fields_for :menu_orders do |i| %>
<div class="field">
<%= i.select :menu_id, options_for_select(Menu.all.pluck(:id)) %>
</div>
<% end %>
<br>
<%= f.submit "Create"%><br>
<% end %>
</div>
OrdersController
class OrdersController < ApplicationController
def new
#order = Order.new
#order.menu_orders.build
end
def create
#order = Order.new(order_params)
if #order.save
redirect_to orders_path
flash[:success] = "Order created"
else
render 'new'
end
end
private
def order_params
params.require(:order).permit(:name, menu_orders_attributes: [ :menu_id, :order_id ])
end
end