Challenge 1: A Role Column — Solution

Migration:
$ rails generate migration AddRoleToUsers role:integer

# db/migrate/20260105000000_add_role_to_users.rb
class AddRoleToUsers < ActiveRecord::Migration[7.1]
  def change
    add_column :users, :role, :integer, default: 0
  end
end

Model:
# app/models/user.rb
class User < ApplicationRecord
  has_secure_password
  enum role: { member: 0, admin: 1 }
end

Controller:
# app/controllers/comments_controller.rb
class CommentsController < ApplicationController
  def destroy
    unless current_user&.admin?
      redirect_to root_path, alert: "Not authorized"
      return
    end

    Comment.find(params[:id]).destroy
    redirect_to root_path
  end
end

=begin
Notes:
- default: 0 on the migration means every existing and newly created user
  defaults to member (0) unless explicitly set to admin (1) -- avoiding a
  situation where existing users end up with a nil role.
- current_user&.admin? uses safe navigation in case current_user itself
  is nil (no one logged in) -- without it, calling .admin? on nil would
  raise NoMethodError instead of cleanly failing the authorization check.
- return after the redirect_to inside the unless block is important --
  without it, execution would continue into the destroy logic below even
  after already redirecting, which is the same "guard clause" discipline
  from Ruby Course 2's idioms chapter.
=end