Case / Switch Statement in Ruby

Why is this here?

I always forget how to write case statements and always find myself looking it up. This is my note to future self on how to write case / switch statements in Ruby.

Syntax

Syntax for a case statement is as follows:

case argument when condition # do stuff else # do stuff if nothing else meets the condition end 

"Else" is optional and represents the "default" case.

All case statements written in this syntax are compared with the === operator so be aware of that! === has slightly different semantics from == which can be found here:

This same === feature is what allows us to compare Regexs on Strings and other cool behavior. === is overriden by individual modules but is usually aliased to ==

Basic statement

arg = "blah" case arg when /blah/ puts "woah, what a blah!" else puts "Theres no blah here!" end 

Adding multiple conditionals

def fruit_identifier(fruit) case fruit when "orange", "grapefruit" puts "Woah! Thats some good citrus!" when "apple", "banana", "pear" puts "Just some normal fruits. Nothing to see here." end end 

One liners

def one_line_case case "only_one" when "only_one" then puts "Look ma! One line!" end end 

if / else syntax

a = 2 case when a == 1, a == 2 puts "a is one or two" when a == 3 puts "a is three" else puts "I don't know what a is" end 

Further Reading

https://www.rubyguides.com/2015/10/ruby-case/

https://ruby-doc.org/core-2.7.3/doc/syntax/control_expressions_rdoc.html#label-case+Expression