param is missing or the value is empty: - ruby-on-rails

Question

When going on the view page, the error "param is missing or the value is empty: restaurant" is displayed.
- I solve the problem by deleting "require(:restaurant)" but don't really understand the trick...do you ?
- I am looking for a solution that allows me to keep the "require(:restaurant)... Any Idea ?
restaurants_controller.rb
class RestaurantsController < ApplicationController
before_action :set_restaurant, only: [:show, :edit, :update]
def index
#restaurants = Restaurant.all
end
def show
end
def new
#restaurant = Restaurant.new(params.permit(:name, :address, :category))
end
def create
#restaurant = Restaurant.new(restaurant_params)
#restaurant.save
redirect_to restaurant_path(#restaurant)
end
private
def set_restaurant
#restaurant = Restaurant.find(params[:id])
end
def restaurant_params
params.require(:restaurant).permit(:name, :address, :category)
end
end
new.html.erb
<%= simple_form_for(#restaurant) do |f| %>
<% if #restaurant.errors.any? %>
<div class="errors-container">
<ul>
<% #restaurant.errors.full_messages.each do |message| %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>
<%= f.input :name %>
<%= f.input :address %>
<%= f.input :category %>
<%= f.submit "add a resto", class: "btn btn-primary" %>
<% end %>
restaurant.rb
class Restaurant < ApplicationRecord
validates :name, :address, :category, presence: true
validates :category, inclusion: { in: ["chinese", "italian", "japanese", "french", "belgian"]}
has_many :reviews, dependent: :destroy
end
routes
Rails.application.routes.draw do
resources :restaurants, only: [:new, :create, :show, :index] do
resources :reviews, only: [ :new, :create ]
end
end

Answer 1

The inputs of your form should be named like this:
restaurant[name]
restaurant[address]
restaurant[category]
It could be that it is something like is:
name
address
category
You can debug your params by inspecting it.
You could do something like this in your restaurant_params in the controller:
raise params.inspect
Or open your debug console of the browser and see what is posted.
And as mentioned in the comments you can use the restaurant_params in your new method but I don't think that fixes you issue it is more likely that the form is the problem.
# instead of
Restaurant.new(params.permit(:name, :address, :category))
# do
Restaurant.new(restaurant_params)

Answer 2

I assume you're trying to auto-populate the form on your new view with some passed attributes.
Your restaurant#new is looking for a params[:restaurant] hash to create a new Restaurant object and can't find it. Look at how you're calling the new action and what parameters are being passed -- my guess is that you're not passing any or you're passing them in the root params hash like params[:name], params[:address] instead of params[:restaurant] => { :name => 'name'}.
Most new actions are a GET so if you're using inline URL parameters put them in like http://address.com/restaurant/new?restaurant[name]=Bistro&restaurant[category]=burgers

Answer 3

In restaurants_controller.rb, we can declare a method for show like:
def show
#restaurant = Restaurant.find(params[:id])
end
In the View Section where we want to link with a button, we can paste
<td><%= link_to "Show", restaurant %> </td>
I hope it will work