Using a controller variable in application html.erb - ruby-on-rails

Question

I'm probably trying too hard for my first website but i wanted to make a dropdown on a (bootstrap) navbar to be flexible, and show the names of the saved work categories.
This is what i've tried to do in the application.html.erb file :
<ul class="dropdown-menu">
<% #workcategory.each do |workcategory| %>
<li><%= workcategory.name%></li>
<% end %>
Failed with error undefined methodeach' for nil:NilClasson the<% #workcategory.each do |workcategory| %>` line.
This is the workcategories controller :
class WorkcategoriesController < ApplicationController
before_action :find_workcategory, only: [:edit, :update, :destroy]
def index
#workcategories = Workcategory.all.order("created_at DESC")
end
def new
#workcategory = Workcategory.new
end
def create
#workcategory = Workcategory.new(post_params)
if #workcategory.save
flash[:notice] = "Workcategory created"
redirect_to(:action=>'index', :workcategory_id => #workcategory.id)
else
#workcategories = Workcategories.order()
render('new')
end
end
def edit
end
def update
end
def destroy
#workcategory.destroy
redirect_to workcategory_path
end
private
def find_workcategory
#workcategory=Workcategory.find(params[:id])
end
def post_params
params.require(:workcategory).permit(:name)
end
end
Any tips and help are welcome, even non-related to the initial question :) Thank you

Answer 1

If you want it in all ur actions, it is wise to put it in your application_controller.rb.
before_filter :set_work_categories
def set_work_categoriers
#w_categories = Workcategory.all.order("created_at DESC")
end
This should work fine.
Also, a tip.
You can use default_scope {order(created_at: :desc)} in your model WorkCategory.rb
Then you can use this like,
def set_work_categoriers
#w_categories = Workcategory.all
end
I would recommend changing the variable name to #w_categories or else it will conflict with your #work_categories name in index action.
In your application.html.erb file, change
<% unless #w_categories.nil? %>
<ul class="dropdown-menu">
<% #w_categories.each do |workcategory| %>
<li><%= workcategory.name%></li>
<% end %>
</ul>
<%end>
I guess this should do the trick

Answer 2

If we talk about index action, then you just forgot to use appropriate variable:
<ul class="dropdown-menu">
<% #workcategories.each do |workcategory| %>
<li><%= workcategory.name%></li>
<% end %>
Update
If you want to have this in all actions, then initialize #workcategories in before_action:
# your_controller.rb
before_action :initialize_work_categories
def initialize_work_categories
#workcategories = Workcategory.all.order("created_at DESC")
end

Answer 3

Layouts
application.html.erb is a layout, meaning that it will be present regardless of whether you're using the Workcategories controller or not.
If you want to load a variable into the layout, irrespective of which controller is being invoked, you'll need to make sure the #workcategory variable is present.
To do this, you would generally put the #workcategory declaration into the ApplicationController (which most other controllers inherit from):
#app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
before_action :set_categories
private
def set_categories
#workcategory = ....
end
end
This is the standard way to populate layout-side variables. It's not efficient and only works if your controllers inherit from the Application controller.
Some further pointers would include the following:
1. Object orientation
Ruby, and by virtue, Rails, is object orientated.
This means that everything you do should revolve around objects. This is why Rails has many helpers that seem to work "magically".
They're not magic at all - they just take the objects you pass them, and build pre-baked HTML to give you specific functionality.
A good example are the routes:
#config/routes.rb
resources :controller
The reason this is important is that when you call actions / variables, you need to think of them as objects. This is difficult to do for newbies, but if you can get your head around it, it helps your coding massively.
--
2. Controllers
Following on from the above, you have to remember that your controller is really just a way to manipulate objects.
Thus, if you're calling #workcategory, you need to appreciate where the object is going to come from and how it's going to be populated.

Answer 4

You can make a helper method work_categories and use that. Either define it directly in application_helper - or if you don't want to use helpers you can put this code in your ApplicationController
class ApplicationController < ActionController::Base
def work_categories
Workcategory.all.order("created_at DESC")
end
helper_method :work_categories
end
Then in your view:
<ul class="dropdown-menu">
<% work_categories.each do |workcategory| %>
<li><%= workcategory.name%></li>
<% end %>
</ul>