Route parameters in Ruby on Rails - Mini Project: Build & Apply

Route parameters

📖 Scenario: You are building a simple Rails app that shows details about books. Each book has a unique ID. You want to create a route that uses this ID in the URL to show the right book.

🎯 Goal: Build a Rails route that uses a route parameter called :id to capture the book's ID from the URL and pass it to the controller.

📋 What You'll Learn

Create a route with a parameter named :id in config/routes.rb

Define a controller action show in BooksController

Use the route parameter params[:id] inside the show action

Add a view file to display the book ID

💡 Why This Matters

🌍 Real World

Web apps often show details for items like products, users, or posts by using route parameters in the URL.

💼 Career

Understanding route parameters is essential for building dynamic web pages and APIs in Rails development jobs.

1

Create the books data hash

Create a hash called BOOKS in app/controllers/books_controller.rb with these exact entries: 1 => 'The Hobbit', 2 => '1984', 3 => 'Pride and Prejudice'.

Ruby on Rails

# Your code here

Need a hint?

Think of BOOKS as a small dictionary that stores book names by their IDs.

2

Add the route with parameter :id

In config/routes.rb, add a route that maps GET /books/:id to the show action of BooksController.

Ruby on Rails

class BooksController  'The Hobbit', 2 => '1984', 3 => 'Pride and Prejudice'}
end

# Your code here

Need a hint?

Use get '/books/:id', to: 'books#show' to capture the :id from the URL.

3

Define the show action using params[:id]

In BooksController, define a show method that sets @book_name to the value from BOOKS using params[:id].to_i.

Ruby on Rails

class BooksController  'The Hobbit', 2 => '1984', 3 => 'Pride and Prejudice'}

  # Your code here
end

Rails.application.routes.draw do
  get '/books/:id', to: 'books#show'
end

Need a hint?

Use params[:id].to_i to convert the route parameter to a number and find the book.

4

Create the show view to display the book name

Create a file app/views/books/show.html.erb with this exact content: <h1>Book: <%= @book_name %></h1>.

Ruby on Rails

class BooksController  'The Hobbit', 2 => '1984', 3 => 'Pride and Prejudice'}

  def show
    @book_name = BOOKS[params[:id].to_i]
  end
end

Rails.application.routes.draw do
  get '/books/:id', to: 'books#show'
end

# Your code here in app/views/books/show.html.erb

Need a hint?

This view shows the book name inside an <h1> heading.