String Interpolation & Manipulation
Master Ruby's powerful string features. Learn interpolation, escape sequences, heredocs, and essential string manipulation methods.
String Interpolation
Interpolation: Use #{} to embed Ruby expressions inside double-quoted strings.
Basic Interpolation Examples
# Basic variable interpolation
name = "Ruby"
age = 30
puts "Hello, #{name}!" # => "Hello, Ruby!"
puts "#{name} is #{age} years old" # => "Ruby is 30 years old"
# Expression interpolation
puts "2 + 3 = #{2 + 3}" # => "2 + 3 = 5"
puts "Today is #{Time.now}" # => "Today is 2024-01-15 10:30:00"
# Method calls in interpolation
text = "hello world"
puts "Uppercase: #{text.upcase}" # => "Uppercase: HELLO WORLD"
puts "Length: #{text.length}" # => "Length: 11"
Escape Sequences
Escape Sequences: Special characters that start with backslash (\) to represent non-printable characters or special meanings.
Common Escape Sequences
# Common escapes
puts "Line 1\nLine 2" # newline
puts "Tab\tSeparated" # tab
puts "Quote: \"Hello\"" # double quote
puts "Backslash: \\" # backslash
puts "Bell: \a" # bell/alert
puts "Return: \r" # carriage return
Unicode Escapes
# Unicode escapes
puts "\u{1F600}" # 😀
puts "\u{1F44D}" # 👍
puts "\u{2764}" # ❤
puts "\u{00A9}" # ©
puts "\u{00AE}" # ®
Heredocs - Multi-line Strings
Heredocs: A way to write multi-line strings that preserve formatting and support interpolation.
Heredoc Examples
# Basic heredoc
message = <<~TEXT
This is a multi-line
string with heredoc.
It preserves formatting!
TEXT
# Heredoc with interpolation
name = "Ruby"
email = <<~EMAIL
Dear #{name},
Welcome to our platform!
Best regards,
The Team
EMAIL
# Different heredoc delimiters
sql = <<~SQL
SELECT * FROM users
WHERE active = true
SQL
Essential String Methods
Case Methods
# Case methods
text = "Hello World"
puts text.upcase # => "HELLO WORLD"
puts text.downcase # => "hello world"
puts text.capitalize # => "Hello world"
puts text.swapcase # => "hELLO wORLD"
Search Methods
# Search methods
text = "Hello World"
puts text.include?("World") # => true
puts text.start_with?("Hello") # => true
puts text.end_with?("World") # => true
puts text.index("World") # => 6
Manipulation Methods
# Manipulation
text = " hello world "
puts text.strip # => "hello world"
puts text.reverse # => " dlrow olleh "
puts text.split # => ["hello", "world"]
puts text.gsub(" ", "-") # => "--hello-world--"
Formatting Methods
# Formatting
text = "hello"
puts text.center(10) # => " hello "
puts text.ljust(10) # => "hello "
puts text.rjust(10) # => " hello"
puts text.ljust(10, "*") # => "hello*****"
String Comparison & Equality
String Comparison Examples
# String comparison
str1 = "hello"
str2 = "hello"
str3 = "Hello"
puts str1 == str2 # => true
puts str1 == str3 # => false
puts str1.eql?(str2) # => true
puts str1.equal?(str2) # => false (different objects)
# Case-insensitive comparison
puts str1.casecmp(str3) # => 0 (equal)
puts str1.casecmp("world") # => -1 (less than)
Best Practices
String Best Practices
- Use double quotes for interpolation: Single quotes are literal
- Prefer heredocs for multi-line strings: Better readability
- Use strip for user input: Remove leading/trailing whitespace
- Be careful with string mutability: Methods return new strings
- Use appropriate comparison methods: == vs eql? vs equal?
Common Mistakes to Avoid
- Forgetting string immutability: Methods don't modify the original
- Using single quotes for interpolation: Won't work as expected
- Not handling nil in interpolation: Can cause errors
- Ignoring encoding issues: Be aware of character encoding
- Overusing string concatenation: Use interpolation instead
Practice Exercises
1 Basic String Interpolation
Create a greeting message using string interpolation:
# Create variables and use interpolation
name = "Alice"
age = 25
puts "Hello, #{name}! You are #{age} years old."
# => "Hello, Alice! You are 25 years old."
2 Math in Strings
Perform calculations inside string interpolation:
# Do math inside interpolation
price = 19.99
tax_rate = 0.08
puts "Price: $#{price}, Tax: $#{price * tax_rate}, Total: $#{price + (price * tax_rate)}"
# => "Price: $19.99, Tax: $1.5992, Total: $21.5892"
3 Method Calls in Interpolation
Call methods inside string interpolation:
# Call methods inside interpolation
text = "hello world"
puts "Original: #{text}, Uppercase: #{text.upcase}, Length: #{text.length}"
# => "Original: hello world, Uppercase: HELLO WORLD, Length: 11"
4 Complex Interpolation
Create a detailed report using multiple interpolations:
# Create a detailed report
student = "Bob"
score = 85
max_score = 100
percentage = (score.to_f / max_score * 100).round(1)
puts "Student: #{student}\nScore: #{score}/#{max_score} (#{percentage}%)\nGrade: #{score >= 90 ? 'A' : score >= 80 ? 'B' : 'C'}"
Try It Yourself
Practice Makes Perfect! Try these exercises in the code runner below:
- Create a personal introduction using your name and age
- Build a shopping receipt with item prices and totals
- Make a weather report with temperature and conditions
- Create a student report card with grades and averages
Try It Yourself
Now practice what you've learned! Use the code editor below to try the exercises above and experiment with string interpolation.
- Start with the practice exercises above - try each one!
- Remember: use
#{}for interpolation, not${} - You can do math inside interpolation:
puts "Total: #{10 + 5}" - Call methods inside interpolation:
puts "Name: #{name.upcase}"
What's Next?
Continue Your Ruby Journey
- Learn Symbols: Understand Ruby's symbol system and immutability
- Explore Regular Expressions: Master pattern matching with strings
- Study Collections: Learn about arrays and hashes
- Practice String Methods: Build projects using string manipulation
- Advanced Topics: Explore encoding, internationalization, and performance
Try It Yourself - Interactive Practice
Learning Tip: The best way to master string interpolation is through hands-on practice! Try these examples and experiment with different variables and expressions!
Interactive Code Runner
Ruby Code Editor
Output will appear here when you run the code...