How to avoid same instance variables for footer - ruby-on-rails

Question

I have a footer in my rails application that shows all recent posts and categories produced by two instances variables in the welcome_controller.rb
But then if i go to another section that has a different controller responsible i get an error as the #posts and #categories instance variables are not there to loop through and list the latest posts and categories.
welcome_controller.rb (code extract)
#categories = Category.all
#posts = Post.order("created_at DESC")
_footer.html
<div class="row footer-black">
<div class="large-3 columns text-left">
<h4>Categories</h4>
<ul>
<% #categories.each do |c| %>
<% unless c.header? %>
<% if c.restriction %>
<% if check_for_free_questions_in_restricted_category(c) %>
<li> <%= link_to c.title, category_random_free_question_path(c),'data-no-turbolink' => true %> </li>
<% else %>
<li> <%= link_to c.title, new_subscription_path,'data-no-turbolink' => true %> </li>
<% end %>
<% else %>
<li> <%= link_to c.title, category_random_question_path(c),'data-no-turbolink' => true %> </li>
<% end %>
<% end %>
<% end %>
</ul>
</div>
<div class="large-5 columns text-left">
<h4>Latest Posts</h4>
<ul>
<% #posts.each do |p| %>
<li> <%= link_to truncate(p.title, length:70), blog_post_path(p) %> </li>
<% end %>
</ul>
</div>
<div class="large-4 columns text-left social-links">
<h4>Social</h4>
<a href="#">
<i class="fa fa-facebook-square fa-2x"></i>
</a>
<a href="#">
<i class="fa fa-twitter-square fa-2x"></i>
</a>
<a href="#">
<i class="fa fa-google-plus-square fa-2x"></i>
</a>
</div>
</div>
is there a way to show categories and posts in footer without instantiating same variables over and over again?

Answer 1

The short answer is 'no'. Every variable must be instantiated (initialized) before it can be used (in this case, in your view).
Now, there are some more efficient ways of instantiating these variables than writing:
#categories = Category.all
#posts = Post.order("created_at DESC")
in multiple controllers. But, that's a different question. If you're interested in that, then ask a new question or refine this one.