Write a Switch Statement in Ruby

1. Match Ranges in Ruby switch
2. Match Regex in Ruby switch
3. Match Proc in Ruby switch

Similar to how the if statement works, the switch statement allows us to control the execution of a code based on some specific condition. This tutorial will look at how the switch statement is used in Ruby.

Below is the syntax for a switch statement in Ruby.

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

We will be looking at some common basic ways of using it and then some somewhat complex examples that are not so common.

Example Codes:

def continent_identifier(country)
  case country
  when "Nigeria"
    puts "Africa"
  when "Netherlands"
    puts "Europe"
  when "India"
    puts "Asia"
  else
    puts "I don't know"
  end
end

continent_identifier("India")
continent_identifier("Netherlands")
continent_identifier("Germany")

Output:

Asia
Europe
I don't know

Above is a basic example of a method that uses a switch statement to identify a country’s continent. Looking at the above example, the following are worth noting.

• Unlike the switch statement in most other programming languages, Ruby’s switch statement does not require break at the end of each when.
• Ruby’s switch statement allows us to specify multiple values for each when so we can return a result if our variable matches any of the values. An example is shown below.

Example Codes:

def continent_identifier(country)
  case country
  when "Nigeria"
    puts "Africa"
  when "Netherlands", "Germany"
    puts "Europe"
  when "India"
    puts "Asia"
  else
    puts "I don't know"
  end
end

continent_identifier("India")
continent_identifier("Netherlands")
continent_identifier("Germany")

Output:

Asia
Europe
Europe

Ruby’s switch statement under the hood uses === operator to do the comparison between the case variable and the values supplied, i.e value === argument. As a result, Ruby switch allows us to make more clever comparisons.

Match Ranges in Ruby switch

In this example, we check if the supplied case variable is included in any of the Ranges specified.

Example Codes:

def check_number(n)
  case n
  when 1..5
    puts "Falls between 1 & 5"
  when 6..10
    puts "Falls between 6 & 10"
  end
end

check_number(3)
check_number(7)

Output:

Falls between 1 & 5
Falls between 6 & 10

Match Regex in Ruby switch

We can also match regular expressions against the case variable, and that’s shown in the example below.

Example Codes:

def month_indentifier(month)
  case month
  when /ber$/
    puts "ends with 'ber'"
  when /ary$/
    puts "ends with 'ary'"
  end
end

month_indentifier("February")
month_indentifier("November")

Output:

ends with 'ary'
ends with 'ber'

Match Proc in Ruby switch

A Ruby Proc encapsulates a block of code that can be stored in a variable or passed around. You can check here for more explanation about Ruby Proc. The following example shows how can use a Ruby Proc in a switch statement.

Example Codes:

def check_number(number)
  case number
  when -> (n) { n.even? }
    puts "It's even"
  when -> (n) { n.odd? }
    puts "It's odd"
  end
end

check_number(3)
check_number(6)

Output:

It's odd
It's even