Rails - create child record from parent

Question

Feel like an idiot for asking this, but I'm starting to feel like I learned it the wrong way originally.

I might note that I'm not using nested routes.

If I have two models:

class Category < ActiveRecord::Base
  has_many :products
end

class Product < ActiveRecord::Base
  belongs_to :category
end

What is the best way to create a new product from the appropriate parent category page?

At the moment I have this on the category page

<%= link_to new_product_path(:category_id => @category) 

Then on the new product page Im using:

<%= form_for @product do |p| %>
  <%= p.hidden_field :category_id, :value => params[:category] %>
  #rest of fields
  #etc
<% end %>

This will work as long as the url parameter survives. However, as soon as the user arrives on this page via the back button or the render 'new' as a result of failed validation, the url parameter is lost and this no longer works.

This is such a simple everyday rails task, there has to be a more reliable method of creating child records from the parent page.

Answer 1

You can change your new and create actions to work similar to as if they were a nested category-product resources, by:

resources :products, except: [:new, :create] do
  get  :new, path: 'products/:category_id/new'
  post :create, path: 'products/:category_id'
end

You would still have to do:

<%= link_to new_product_path(:category_id => @category) %>

But you will not have to add the hidden fields in your form. Instead in your create action inside your controller you can do:

category = Category.find params[:category_id]
category.products.build(product_params)

Doing it this way you will not be utilizing url parameters, and failed validations should prompt you back to the proper page.

Answer 2

All instance variables you define in your controller action are present in the view. So if you define @category in your controller you can access it in the view using <%= @category %> . This way you can avoid using params inside your view.

def new 
  @category = Category.find(params[:category])

def create
  @category = Category.find(params[:category])

<%= form_for @product do |p| %>
  <%= p.hidden_field :category_id, :value => @category.id %>