Nil as the absence of value in Ruby - Mini Project: Build & Apply

Nil as the absence of value

📖 Scenario: Imagine you are managing a list of people and their favorite colors. Sometimes, a person might not have a favorite color yet. In Ruby, nil is used to show that something has no value.

🎯 Goal: You will create a Ruby program that uses nil to represent missing favorite colors and then check for those missing values.

📋 What You'll Learn

Create a hash called people_colors with exact keys and values

Use nil to represent no favorite color

Create a variable called missing_color_count to count how many people have no favorite color

Use a for loop with variables person and color to iterate over people_colors

Print the number of people with no favorite color using puts

💡 Why This Matters

🌍 Real World

In real programs, <code>nil</code> helps show when information is missing or unknown, like a missing phone number or address.

💼 Career

Understanding <code>nil</code> is important for Ruby developers to handle data correctly and avoid errors when values are missing.

1

Create the people_colors hash

Create a hash called people_colors with these exact entries: 'Alice' => 'blue', 'Bob' => nil, 'Charlie' => 'green', 'Diana' => nil

Ruby

# Create the people_colors hash with exact entries
# Your code here

Need a hint?

Use curly braces {} to create a hash. Use nil for missing favorite colors.

2

Create a counter for missing colors

Create a variable called missing_color_count and set it to 0 to count people with no favorite color

Ruby

people_colors = { 'Alice' => 'blue', 'Bob' => nil, 'Charlie' => 'green', 'Diana' => nil }
# Create missing_color_count and set it to 0
# Your code here

Need a hint?

Just set missing_color_count to zero to start counting.

3

Count how many people have no favorite color

Use a for loop with variables person and color to iterate over people_colors. Inside the loop, increase missing_color_count by 1 if color is nil

Ruby

people_colors = { 'Alice' => 'blue', 'Bob' => nil, 'Charlie' => 'green', 'Diana' => nil }
missing_color_count = 0
# Use a for loop to count nil colors
# Your code here

Need a hint?

Use color.nil? to check if the color is missing.

4

Print the count of missing favorite colors

Use puts to print the value of missing_color_count

Ruby

people_colors = { 'Alice' => 'blue', 'Bob' => nil, 'Charlie' => 'green', 'Diana' => nil }
missing_color_count = 0
for person, color in people_colors
  if color.nil?
    missing_color_count += 1
  end
end
# Print missing_color_count
# Your code here

Need a hint?

Use puts missing_color_count to show the number of people without a favorite color.