Ruby - Case Statement

The Case statement in Ruby language is used to execute one of many code statements. It can be considered as group of If-else statements.

Syntax

case expression
when expression 1 [then]
  statement 1
when expression 2 [then]
  statement 2
  ...
  ...
  ...
when expression n [then]
  statement n
else
  default statement
end

The case expression is evaluated and matched with when expressions. When it matches, the following when block of code is executed.

Example:

In the example below, the case expression is a variable called i with value 2 which is matched against when expressions. When it matches with the when expression, the following block of code is executed.

i = 2

case i
when 1
  puts "Red"
when 2
  puts "Blue"
when 3
  puts "Green"
end

The output of the above code will be:

Blue

else statement

The else Statement can also be used with case statement. It is executed when there is no match between any when expressions.

Example:

In the example below, the case expression is a variable called i with value 10 which is matched against when expressions. As there is no match, the else block of code gets executed.

i = 10

result = case i
when 1 then "Red"
when 2 then "Blue"
when 3 then "Green"
else "No match found."
end

puts result

The output of the above code will be:

No match found.

Common code blocks

There are instances where same code block is required in multiple when expression.

Example:

In the example below, same code block is shared for different when expressions.

i = 10

result = case i
when 1 
  "Red"
when 2, 10 
  "Blue"
when 3, 4
  "Green"
end

puts result

The output of the above code will be:

Blue