Select and pluck in Ruby on Rails - Mini Project: Build & Apply

Select and Pluck in Rails

📖 Scenario: You are building a simple Rails app to manage a bookstore. You have a list of books stored in the database with details like title, author, and price.You want to practice extracting specific information from the books using Rails ActiveRecord methods.

🎯 Goal: Learn how to use select to filter records and pluck to extract specific fields from the database in Rails.

📋 What You'll Learn

Create a Book model with attributes: title (string), author (string), price (integer)

Use select to filter books priced above a certain amount

Use pluck to get a list of book titles from the filtered books

💡 Why This Matters

🌍 Real World

Filtering and extracting specific data from a database is common in web apps like bookstores, inventory systems, or user management.

💼 Career

Understanding select and pluck helps you write efficient Rails queries to get exactly the data you need without extra processing.

1

Create the books data

Create a variable called books and assign it an array of hashes representing books with these exact entries: { title: 'Ruby Basics', author: 'Alice', price: 30 }, { title: 'Rails Advanced', author: 'Bob', price: 50 }, { title: 'JavaScript Guide', author: 'Carol', price: 40 }.

Ruby on Rails

# Create the books array with hashes
# Your code here

Need a hint?

Use an array of hashes with the exact keys and values given.

2

Set the price threshold

Create a variable called price_threshold and set it to 35.

Ruby on Rails

books = [
  { title: 'Ruby Basics', author: 'Alice', price: 30 },
  { title: 'Rails Advanced', author: 'Bob', price: 50 },
  { title: 'JavaScript Guide', author: 'Carol', price: 40 }
]
# Set the price threshold
# Your code here

Need a hint?

Just assign the number 35 to the variable price_threshold.

3

Filter books with select

Create a variable called expensive_books and assign it the result of using select on books to keep only books where the price is greater than price_threshold.

Ruby on Rails

books = [
  { title: 'Ruby Basics', author: 'Alice', price: 30 },
  { title: 'Rails Advanced', author: 'Bob', price: 50 },
  { title: 'JavaScript Guide', author: 'Carol', price: 40 }
]
price_threshold = 35
# Use select to filter expensive books
# Your code here

Need a hint?

Use select with a block that checks if book[:price] is greater than price_threshold.

4

Extract titles with pluck

Create a variable called titles and assign it the result of using pluck on expensive_books to get an array of their title values.

Ruby on Rails

books = [
  { title: 'Ruby Basics', author: 'Alice', price: 30 },
  { title: 'Rails Advanced', author: 'Bob', price: 50 },
  { title: 'JavaScript Guide', author: 'Carol', price: 40 }
]
price_threshold = 35
expensive_books = books.select { |book| book[:price] > price_threshold }
# Use pluck to get titles
# Your code here

Need a hint?

Use map with a block to extract the :title from each book hash.