How do I create a page without a model? - ruby-on-rails

Question

I'm working on an app which has many 'Activities'. Each 'Activity' has many 'Ranks'. I'd like each 'Activity' to have a page called grading, where the user can see a list of all of that activity's ranks and conveniently update them. I imagine the URL would be something like http://localhost:3000/activities/21/grading
I'm already using http://localhost:3000/activities/21/edit for its intended purpose.
I don't need a model for gradings, as I don't need to save any grading records.
I know exactly what to put in the view, I'm just unsure what to add to the controller and routes files. Other people have worked on this app but I'm unable to contact them.
Routes
resources :activities do
collection do
get 'scheduled_classes'
end
end
resources :ranks
end
activities_controller
class ActivitiesController < ApplicationController
def new
#activity = Activity.new
#activity.timeslots.build
#activity.ranks.build
end
def create
#activity = current_club.activities.new(activity_params)
if #activity.save
flash[:success] = "New class created!"
redirect_to activity_path(#activity)
else
render 'new'
end
end
def edit
#activity = current_club.activities.find_by(id: params[:id])
#active_ranks = #activity.ranks.where(active: true)
if !#activity.active?
redirect_to activities_path
else
#activity.timeslots.build
end
end
def update
#activity = current_club.activities.find_by(id: params[:id])
if #activity.update_attributes(activity_params)
flash[:success] = "Class updated!"
redirect_to edit_activity_path(#activity)
else
render 'edit'
end
end
def show
#activity = current_club.activities.find_by(id: params[:id])
#active_ranks = #activity.ranks.where(active: true)
if #activity.nil?
redirect_to root_url
elsif !#activity.active?
redirect_to activities_path
end
end
def index
#activities = current_club.activities.all
end
def destroy
#activity = current_club.activities.find_by(id: params[:id])
if #activity.nil?
redirect_to root_url
else
#activity.destroy
flash[:success] = "Class deleted"
redirect_to activities_path
end
end
end
private
def activity_params
params.require(:activity).permit(:name, :active,
:timeslots_attributes => [:id,
:time_start,
:time_end,
:day,
:active,
:schedule],
:ranks_attributes => [:id,
:name,
:position,
:active])
end
end
activity
class Activity < ApplicationRecord
belongs_to :club
has_many :timeslots, dependent: :destroy
accepts_nested_attributes_for :timeslots,:allow_destroy => true
has_many :ranks, dependent: :destroy
has_many :attendances, dependent: :destroy
accepts_nested_attributes_for :ranks
validates :club_id, presence: true
validates :name, presence: true, length: { maximum: 50 }
end

Answer 1

Your routes don't need to have an associated model or resource.
resources :activities do
collection do
get 'scheduled_classes'
end
member do
get :grading
end
end
will match to activities#grading
See https://guides.rubyonrails.org/routing.html#adding-member-routes for more info.

Answer 2

As you want to add a route on a particular activity, you should add member route on the activity like below,
resources :activities do
collection do
get 'scheduled_classes'
end
get :grading, on: :member
end
Apart from this, you have to add method in ActivitiesController for this route like below,
def grading
#activity = Activity.find_by(id: params[:id])
# do more here
end
In view files, you can create grading.html.erb under activities resources and put your view code there.