undefined method 'each' when accessing articles from navbar in rails app - ruby-on-rails

Question

I need to be able to access articles through the navbar dropdown.
in my views/application/_navbar.html.erbI have the code snipped below. It is not working and I always get this error undefined method 'each' for nil:NilClass
when I hit the link in the dropdown the app goes to the right path http://localhost:3000/lcas/1
I only need to be able to access the first article in each category so http://localhost:3000/lcas/1 is the right path for the first link in the dropdown
code from views/application/_navbar.html.erb
<ul class="dropdown-menu">
<% #lcas.each do |lca| %>
<li><%= link_to lca.title, lca_path(lca) %></li>
<% end %>
<% #energy_analyses.each do |energy_analysis| %>
<li><%=link_to energy_analysis.title, energy_analysis_path(energy_analysis) %></li>
<% end %>
<% #green_accountings.each do |green_accounting| %>
<li><%= link_to green_accounting.title, green_accounting_path(green_accounting) %></li>
<% end %>
<li class="divider"></li>
<li>Something</li>
<li class="divider"></li>
<li>something</li>
</ul>
On my index.html.erbI have basically the same code and there it works.
<% #lcas.each do |lca| %>
<div class="col-md-4 col-xs-12">
<span class="glyphicon glyphicon-tasks icons" aria-hidden="true"> </span>
<div class="panel-heading">
<h3 class="panel-title"><%= link_to lca.title, lca_path(lca) %></h3>
</div>
</div>
<% end %>
I've tried to add
#lcas = Lca.all
#energy_analyses = EnergyAnalysis.all
#green_accountings = GreenAccounting.all
to the application_controller.rb but with out any success.
here is the lcas_controller.rb
class LcasController < InheritedResources::Base
private
def lca_params
params.require(:lca).permit(:title, :body, :image)
end
end
It would be very nice if someone could guide me through this.

Answer 1

You probably need few things:
Set a before_action method for those variables in application_controller.rb to make sure each other controller calls it and pass the variable to their corresponding view:
before_action :set_vars
def set_vars
#lcas = Lca.all
#energy_analyses = EnergyAnalysis.all
#green_accountings = GreenAccounting.all
end
Now you should be able to access #lcas from your partial, but using instance variables in partials is violating MVC, so you should pass locals to it:
<%= render 'application/navbar', :lcas => #lcas %>
Not sure how to pass multiple locals, maybe like this:
<%= render 'shared/navbar', locals: {:lcas => #lcas, :energy => #energy_analyses, :green => #green_accountings} %>
And of course, don't use # in partial if passing locals:
<% energy.each do |energy_analysis| %>