Ruby case Statement

case Statement Concepts

case grade
when "A"
  puts "Excellent"
end

case day
when "Sat", "Sun"
  puts "Weekend"
end

case score
when 90..100
  puts "A grade"
end

case value
when 1
  puts "One"
else
  puts "Other"
end

🔹 Basic case Statement

The case statement compares a value against multiple when clauses. When a match is found, that code block executes and the case statement ends. This is cleaner than writing many elsif statements and makes your code easier to read and maintain.

# Simple case statement
grade = "B"

case grade
when "A"
  puts "Excellent!"
when "B"
  puts "Good job!"
when "C"
  puts "Satisfactory"
when "D"
  puts "Needs improvement"
when "F"
  puts "Failed"
else
  puts "Invalid grade"
end
# Output: Good job!

# Another example
traffic_light = "red"

case traffic_light
when "green"
  puts "Go"
when "yellow"
  puts "Slow down"
when "red"
  puts "Stop"
end
# Output: Stop
                            

🔹 Multiple Values in when

You can match multiple values in a single when clause by separating them with commas. This is useful when different values should trigger the same action, like grouping weekdays together or handling similar status codes with one response.

# Multiple values in one when
day = "Saturday"

case day
when "Monday", "Tuesday", "Wednesday", "Thursday", "Friday"
  puts "It's a weekday"
when "Saturday", "Sunday"
  puts "It's the weekend!"
end
# Output: It's the weekend!

# Another example
month = "December"

case month
when "December", "January", "February"
  puts "Winter season"
when "March", "April", "May"
  puts "Spring season"
when "June", "July", "August"
  puts "Summer season"
when "September", "October", "November"
  puts "Fall season"
end
# Output: Winter season
                            

🔹 case with Ranges

Case statements can match ranges, making them perfect for categorizing numeric values. Use ranges in when clauses to check if a value falls within a specific interval, like grading scores or age groups. Ruby checks ranges using the === operator.

# Using ranges in case
score = 85

case score
when 90..100
  puts "Grade: A"
when 80..89
  puts "Grade: B"
when 70..79
  puts "Grade: C"
when 60..69
  puts "Grade: D"
else
  puts "Grade: F"
end
# Output: Grade: B

# Age categories
age = 35

case age
when 0..12
  puts "Child"
when 13..19
  puts "Teenager"
when 20..59
  puts "Adult"
when 60..120
  puts "Senior"
else
  puts "Invalid age"
end
# Output: Adult
                            

🔹 case with Return Values

Case statements return the value of the executed when clause, allowing you to assign the result directly to a variable. This makes code more concise by eliminating the need for separate assignment statements in each branch.

# Assigning case result to variable
day = "Wednesday"

day_type = case day
when "Monday", "Tuesday", "Wednesday", "Thursday", "Friday"
  "Weekday"
when "Saturday", "Sunday"
  "Weekend"
else
  "Unknown"
end

puts day_type  # Output: Weekday

# Another example
temperature = 28

weather = case temperature
when 0..10
  "Cold"
when 11..20
  "Cool"
when 21..30
  "Warm"
else
  "Hot"
end

puts "It's #{weather} today"  # Output: It's Warm today
                            

🔹 case without an Argument

You can use case without specifying a value to compare, making it work like a series of if-elsif statements. Each when clause contains its own condition, providing flexibility for complex logic where different conditions need different comparisons.

# case without argument
score = 75
attendance = 85

result = case
when score >= 90 && attendance >= 90
  "Excellent"
when score >= 80 && attendance >= 80
  "Very Good"
when score >= 70 && attendance >= 70
  "Good"
when score >= 60
  "Pass"
else
  "Fail"
end

puts result  # Output: Good

# Another example
time = 14

greeting = case
when time < 12
  "Good morning"
when time < 18
  "Good afternoon"
else
  "Good evening"
end

puts greeting  # Output: Good afternoon
                            

🔹 Practical case Examples

Case statements shine in real-world scenarios like menu systems, status handlers, and type checkers. They make code more organized and easier to extend when you need to add new options. Here are common patterns you'll use frequently in Ruby applications.

# Menu system
choice = 2

case choice
when 1
  puts "Starting new game..."
when 2
  puts "Loading saved game..."
when 3
  puts "Opening settings..."
when 4
  puts "Exiting game..."
else
  puts "Invalid choice"
end
# Output: Loading saved game...

# HTTP status codes
status_code = 404

message = case status_code
when 200
  "OK"
when 404
  "Not Found"
when 500
  "Internal Server Error"
else
  "Unknown Status"
end

puts message  # Output: Not Found

# Type checking
value = "hello"

case value
when String
  puts "It's a string"
when Integer
  puts "It's a number"
when Array
  puts "It's an array"
else
  puts "Unknown type"
end
# Output: It's a string