How do I make my objects less messy? - ruby-on-rails

Question

My project has three main parts to it:
Pages (similar to articles)
Categories (the pages have a category associated with them)
Tags (each Page can have several different tags)
I have a sidebar which uses #categories to pull through a list of all the current categories in my project:
<div class="col-md-3">
<p class="lead">Categories</p>
<div class="list-group">
<%= link_to 'All articles', pages_path(#page), :class => 'list-group-item' %>
<% #categories.each do |category| %>
<%= link_to category.name, category_path(category), :class => 'list-group-item' %>
<% end %>
</div>
</div>
But currently I need to include
#categories = Category.all
In my index and show actions in my controllers for both pages and categories so that the sidebar loads (I only use the sidebar in these two parts of the project).
Is there an easier way of doing this than including the above code in every action in the controller?
Also with the tags controller after creating a page and going to the tag's show page to view any pages associated with those tags, I get an error saying 'Couldn't find page with 'id'=2.
class TagsController < ApplicationController
def index
#tags = Tag.all
end
def show
#tag = Tag.find(params[:id])
#page = Page.find(params[:id])
#categories = Category.all
end
-
<% #tag.pages.each do |page| %>
<div class="thumbnail">
<div class="text">
<article class="clearfix">
<%= link_to page.title, url_for_page(page), class: "h1" %>
<p class="pull-right"><span class="glyphicon glyphicon-time"></span> Posted on <%= page.created_at.to_formatted_s :long %></p>
<hr />
<%= page.body.html_safe %>
<hr />
<div class="btn-group btn-group-xs" role="group" aria-label="...">
<% page.tags.each do |tag| %>
<%= link_to tag.name, tag_path(tag), class: "btn btn-info" %>
<% end %>
</div>
</article>
</div>
</div>
<% end %>
Anyone got any ideas? Any help would be greatly appreciated :)
Thanks!
Update:
Routes file:
Rails.application.routes.draw do
resources :categories
resources :pages
resources :tags
Models:
Category.rb
class Category < ActiveRecord::Base
has_many :pages
Page.rb
class Page < ActiveRecord::Base
include Bootsy::Container
belongs_to :category
has_many :taggings
has_many :tags, through: :taggings
def tag_list
self.tags.collect do |tag|
tag.name
end.join(", ")
end
def tag_list=(tags_string)
tag_names = tags_string.split(", ").collect{ |s| s.strip.downcase }.uniq
new_or_found_tags = tag_names.collect { |name| Tag.find_or_create_by(name: name) }
self.tags = new_or_found_tags
end
end
Tag.rb
class Tag < ActiveRecord::Base
include Bootsy::Container
has_many :taggings
has_many :pages, through: :taggings
def to_s
name
end
end
Tagging.rb
class Tagging < ActiveRecord::Base
include Bootsy::Container
belongs_to :tag
belongs_to :page
end

Answer 1

You could add a before_action for the controller limited to only index and show actions, as below:
class TagsController < ApplicationController
before_action :load_categories, only: [:index, :show]
# Your code
private
def load_categories
#categories = Category.all
end
end
That will load the categories into the instance variable for both the index and show actions.
For the error you're getting, if I'm reading it right you have nested routes? You need to be getting the correct ID for the tag, which is :tag_id:
def show
#tag = Tag.find(params[:tag_id])
#page = Page.find(params[:id])
#categories = Category.all
end
You were getting :id for both. If that doesn't work, are your routes nested? If not post your routes and I'll update the answer.

Answer 2

You can DRY out your Controller to set page and categories in a callback. But take care: you may omit the categories query in the categories#index action, but your page#... actions may skip the callback at all skip_before_action set_page or better overwrite the method and use a correct handling.
class ApplicationController
before_action set_page, only: [:index, :show]
before_action set_categories, only: [:index, :show]
private
def set_page
#page = Page.find params[:page_id]
end
def set_categories
#categories = Category.all
end
end