Install and create the active storage migrations.

Gemfile

@@ -1,7 +1,7 @@
 source 'https://rubygems.org'
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
-ruby '3.1.4'
+ruby '3.2.2'
 
 # Bundle edge Rails instead: gem "rails", github: "rails/rails", branch: "main"
 gem 'rails', '~> 7.0.8'

app/controllers/api/reservations_controller.rb

@@ -4,7 +4,7 @@ class Api::ReservationsController < ApplicationController
   # GET /reservations
   def index
     user_id = params[:user_id]
-    @reservations = Reservation.includes(:course).where(user_id: user_id)
+    @reservations = Reservation.includes(:course).where(user_id:)
 
     render json: @reservations, include: :course
   end

app/models/course.rb

@@ -2,6 +2,8 @@ class Course < ApplicationRecord
   has_many :reservations
   has_many :users, through: :reservations
 
+  has_one_attached :image
+
   validates :name, presence: true
   validates :description, presence: true
   validates :image, presence: true

db/migrate/20231009122412_create_active_storage_tables.active_storage.rb

@@ -0,0 +1,57 @@
+# This migration comes from active_storage (originally 20170806125915)
+class CreateActiveStorageTables < ActiveRecord::Migration[5.2]
+  def change
+    # Use Active Record's configured type for primary and foreign keys
+    primary_key_type, foreign_key_type = primary_and_foreign_key_types
+
+    create_table :active_storage_blobs, id: primary_key_type do |t|
+      t.string   :key,          null: false
+      t.string   :filename,     null: false
+      t.string   :content_type
+      t.text     :metadata
+      t.string   :service_name, null: false
+      t.bigint   :byte_size,    null: false
+      t.string   :checksum
+
+      if connection.supports_datetime_with_precision?
+        t.datetime :created_at, precision: 6, null: false
+      else
+        t.datetime :created_at, null: false
+      end
+
+      t.index [ :key ], unique: true
+    end
+
+    create_table :active_storage_attachments, id: primary_key_type do |t|
+      t.string     :name,     null: false
+      t.references :record,   null: false, polymorphic: true, index: false, type: foreign_key_type
+      t.references :blob,     null: false, type: foreign_key_type
+
+      if connection.supports_datetime_with_precision?
+        t.datetime :created_at, precision: 6, null: false
+      else
+        t.datetime :created_at, null: false
+      end
+
+      t.index [ :record_type, :record_id, :name, :blob_id ], name: :index_active_storage_attachments_uniqueness, unique: true
+      t.foreign_key :active_storage_blobs, column: :blob_id
+    end
+
+    create_table :active_storage_variant_records, id: primary_key_type do |t|
+      t.belongs_to :blob, null: false, index: false, type: foreign_key_type
+      t.string :variation_digest, null: false
+
+      t.index [ :blob_id, :variation_digest ], name: :index_active_storage_variant_records_uniqueness, unique: true
+      t.foreign_key :active_storage_blobs, column: :blob_id
+    end
+  end
+
+  private
+    def primary_and_foreign_key_types
+      config = Rails.configuration.generators
+      setting = config.options[config.orm][:primary_key_type]
+      primary_key_type = setting || :primary_key
+      foreign_key_type = setting || :bigint
+      [primary_key_type, foreign_key_type]
+    end
+end

db/seeds.rb

@@ -1,32 +1,24 @@
-# This file should contain all the record creation needed to seed the database with its default values.
-# The data can then be loaded with the bin/rails db:seed command (or created alongside the database with db:setup).
-#
-# Examples:
-#
-#   movies = Movie.create([{ name: "Star Wars" }, { name: "Lord of the Rings" }])
-#   Character.create(name: "Luke", movie: movies.first)
 # db/seeds.rb
 
 # Create sample users
 user1 = User.create(name: "John Doe")
 user2 = User.create(name: "Jane Smith")
 
+# Create an array of image URLs
+image_urls = ['/course/database.png', '/course/web.png']
+
 # Create sample courses
-course1 = Course.create(
-  name: "Course 1",
-  description: "Description for Course 1",
-  image: "course1.jpg",
-  fee: 100.0,
-  startDate: Date.new(2023, 10, 10)
-)
-course2 = Course.create(
-  name: "Course 2",
-  description: "Description for Course 2",
-  image: "course2.jpg",
-  fee: 150.0,
-  startDate: Date.new(2023, 11, 5)
-)
+courses = []
+6.times do |i|
+  courses << Course.create(
+    name: "Course #{i + 1}",
+    description: "Description for Course #{i + 1}",
+    image: image_urls[i % 2], # Alternating between the two images
+    fee: 100.0 + (i * 10),     # Incrementing fee
+    startDate: Date.new(2023, 10, 10) + i.days  # Incrementing start date
+  )
+end
 
 # Create sample reservations associated with users and courses
-Reservation.create(user_id: user1.id, course_id: course1.id, city: "New York", date: Date.new(2023, 10, 12))
-Reservation.create(user_id: user2.id, course_id: course2.id, city: "Los Angeles", date: Date.new(2023, 11, 8))
+Reservation.create(user_id: user1.id, course_id: courses[0].id, city: "New York", date: Date.new(2023, 10, 12))
+Reservation.create(user_id: user2.id, course_id: courses[1].id, city: "Los Angeles", date: Date.new(2023, 11, 8))