How to do the calculation without any models in Rails? - ruby-on-rails

Question

I need to get an integer(#integer) from the form in my root_path, do multiplication (#integer*45) and display the result on the same page. How can I do it without any models in my application?
Please, share your best practice. Thank you!
I was trying to do next:
CalculatorsController
def calculation
#integer = params[:integer]
#result = #integer*45
end
def result
end
root.rb
root :to => 'calculators#result'
resources :calculators, :collection=>{:result => :get, :calculation => :post}
calculators/result.html.erb
<% form_tag root_path, :html => {:method => :post} do %>
<%= label_tag 'integer' %>
<%= text_field_tag :integer %>
<div><%= submit_tag 'OK' %></div>
<% end %>

Answer 1

I'll do it with ajax, so there is no need for page refresh:
First, update the routes, for your example you only need two routes, one get (or root) and one post.
routes.rb:
Rails.application.routes.draw do
root 'calculators#result'
post 'calculators/calculation'
end
Next, update your view:
Change the url in your form_tag where the data will be sent (to calculation action instead of result).
Add remote: true option to enable ajax.
Add a tag where you will display your result.
result.html.erb:
<% form_tag calculators_calculation_url, remote: true do %>
<%= label_tag 'integer' %>
<%= text_field_tag :integer %>
<div><%= submit_tag 'OK' %></div>
<% end %>
<div id="total"></div>
And create a view for calculation action, but since you are using ajax, you will create it as js.erb and include the required javascript (or jQuery) to update your view (i'm using jQuery in the example).
calculation.js.erb:
$('#total').html('<%= #result %>')
Now when you click submit, your form will be sent to calculation action and will update the div with #result.

Answer 2

Just add the field to your form...
<% form_tag root_path, :html => {:method => :post} do %>
<%= label_tag 'integer' %>
<%= text_field_tag(:integer, #integer) %>
<% if #result.present? %>
<br>
Result is: <%= #result %>
<br/>
<% end %>
<div><%= submit_tag 'OK' %></div>
<% end %>
And then render result in your calculate...
def calculation
#integer = params[:integer].to_i
#result = #integer*45
render :result
end

Answer 3

Your result view (result.html.erb) is getting its data from the result method, not calculation. Update your controller as follows:
def calculation
#integer = params[:integer]
end
def result
#result = #integer*45
end
You then need a tag to display your result in the view, something like:
<p> <%= #result %> </p>