Creating an association between a source document and each item with nokogiri - ruby-on-rails

Question

I'm building my first web application and am sort of lost. I've read the nokogiri docs, and know that I need to use Nokogiri::XML(open("http://foo")), but I'm not sure where the proper place is to use it.
I have a series model with three columns, :name, :description and :url. I want to have it so when I create a new series, the URL placed in the :url form field is parsed, and creates an episode for each item in the feed, populating its columns with xpath arguments.
Would this logic go in the series model or controller? Or in the episodes model or controller?
Here's what I have now.
series model
class Series < ActiveRecord::Base
validates :name, presence: true
validates :description, presence: true
validates :url, presence: true
has_many :episodes, dependent: :destroy
end
series controller
class SeriesController < ApplicationController
def index
#series_all = Series.all
end
def show
#series = Series.find(params[:id])
end
def new
#series = Series.new
end
def edit
#series = Series.find(params[:id])
end
def create
#series = Series.new(series_params)
if #series.save
redirect_to #series
else
render 'new'
end
end
def destroy
#series = Series.find(params[:id])
#series.destroy
redirect_to series_path
end
private
def series_params
params.require(:series).permit(:name, :description, :url)
end
end
routes.rb
Rails.application.routes.draw do
resources :series do
resources :episodes
end
root 'home#index'
end
series form partial
<%= form_for #series do |f| %>
<div class="series-form">
<div class="series-form__name">
<%= f.label :name %>
<%= f.text_field :name %>
</div>
<div class="series-form__description">
<%= f.label :description %>
<%= f.text_area :description %>
</div>
<div class="series-form__url">
<%= f.label :url %>
<%= f.text_field :url %>
</div>
<div class="series-form__submit">
<%= f.submit %>
</div>
</div>
<% end %>
episodes has an empty controller with no model yet.
Edit: To clarify, I'm trying to import podcasts. So using The Stack Exchange Podcast's RSS feed as an example, I would place this in the series form:
Name: The Stack Exchange Podcast (from channel/title)
Description: Hosted by Joel Spolsky with Jay Hanlon and David Fullerton . . . (from channel/itunes:summary)
URL: https://blog.stackoverflow.com/feed/podcast/
and it would create an episode for each item in the feed. It would be even better if I could grab channel/title and channel/itunes:summary automatically. I hope this is possible and makes sense.

Answer 1

You don't really need Nokogiri for this. Just use the RSS module that comes with Ruby's standard lib.
As to your question, it looks like you want to populate the ActiveRecord model with the information from RSS feed. The simplest way, especially if you are not planning to do this for any other data in your application, is to have controller make the call to RSS and map the data to the Series and Episode model there. It would be cleaner (and easier to test) if you
create special objects that can take the RSS data and generate Series from the channel data and Episodes from the item data.
The next step would be to treat RSS as another form of data storage (much like SQLite or MySQL databases), and create a layer of code that can interact with an RSS end-point and produce a mapped model (say RSSSeries and RSSEpisodes in your case) through an interface similar to ActiveRecord (but read-only, of course). Controller then can be used to fetch the RSSSeries and access related RSSEpisodes translate it to the ActiveRecord Series and Episodes models and save them.