Change label's value on form submit - Ruby on Rails - ruby-on-rails

Question

I am brushing up on my rails. I have a dead simple form. views -> genalg -> index.html.erb
<h1>Genalg#index</h1>
<p>Find me in app/views/genalg/index.html.erb</p>
<%= form_with url: "/calculate" do |form| %>
<%= form.text_field :query %>
<%= form.submit "calculate" %>
<% end %>
<% unless #query.nil? %>
<p><%=#query%></p>
<% end %>
I have a controller under controllers -> genalg_controller.rb
class GenalgController < ApplicationController
def index
#query = "biznass"
end
def calculate
puts params
#query = (params[:query].to_i * 2).to_s
render :index
end
end
In routes.rb:
Rails.application.routes.draw do
get 'genalg/index'
post '/calculate', to: 'genalg#index' , as: 'index'
# For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
end
How, when I fill the from text :query and hit submit, can I get the text denoted at the very end of my view to display the value I put in times 2 (per the calculate function)? Seems like it should be easy but clearly I have forgotten some basic tenant of how forms and form submission works.

Answer 1

Change the render to redirect_to and pass params like this
def calculate
puts params
#query = (params[:query].to_i * 2).to_s
redirect_to index_path(query: #query)
end
<% unless params[:query].blank? %>
<p><%=#query%></p>
<% end %>

Answer 2

Looking at your routes file, you are calling index action on submitting a post request for calculate so its always returns #query value from the index method i.e. biznass
If you want to calculate #query using params and use index action for that with same routes defined, you have to update index method
def index
if params[:query]
puts params
#query = (params[:query].to_i * 2).to_s
else
#query = 'biznass'
end
OR you can change route and controller code
Rails.application.routes.draw do
get 'genalg/index'
post 'genalg/calculate'
# For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
end
class GenalgController < ApplicationController
def index
#query = params[:query] || "biznass"
end
def calculate
puts params
#query = (params[:query].to_i * 2).to_s
redirect_to index_path(query: #query)
end
end

Answer 3

I suggest use resources in your routes.rb instead doing it like that, it will be far more concise, scaleable and you can use url helper method. you can run rake routes in your terminal to see detail of routes, like helper method's name, path, http verb, and which controller's method a path is using.
resources :genalg, controller: :genalg, only: [:index] do
collection do
post :calculate
end
end
in this instance of def calculate, If you have method with http verb POST and it supposed to response with success status, most of the time you need to redirect it instead of rendering it, because in case when user refresh or copy url after calculate, the page will not be found as calculate have POST http verb.
so you have to change render to redirect_to and pass params :query, so every time user refresh the page after calculate, :query will be persisted. even if you want to store :query in database this is still applicable. also, in here you can see we use helper method to redirect to index page by using genalg_index_path
def calculate
puts params
query = (params[:query].to_i * 2).to_s
redirect_to genalg_index_path(query: query)
end
then in index you can check whether params query is empty or not
def index
#query = params[:query] || 'biznass'
end
And in view as you can see we use helper method again to get calculate path, and we don't need #query condition as it never nil
<h1>Genalg#index</h1>
<p>Find me in app/views/genalg/index.html.erb</p>
<%= form_with url: genalg_calculate_path do |form| %>
<%= form.text_field :query %>
<%= form.submit 'calculate' %>
<% end %>
<p><%=#query%></p>