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The Handbook for Ruby Developers

String Interpolation in Ruby

Explore the concept of string interpolation in Ruby to improve program readability. Understand how to evaluate expressions within strings, handle input with newline characters, and use methods like chomp to clean input data. This lesson also compares Ruby's interpolation to JavaScript to deepen your understanding.

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String interpolation

We can significantly improve the readability of a program if we take advantage of string interpolation:

Note: To run the program below, we give our age as input using STDIN, or we can also execute this program in the terminal at the end of the lesson using the command:

$ ruby string_interpolation_example_1.rb
Ruby
# String Interpolation Example code
puts "Your age?"
age = gets.to_i # Get age as input from user
age_months = age * 12 # Multiply age with 12 to convert into months
puts "Your age is #{age_months}" # string interpolation using curly brackets
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Explanation

There is no need for typecasting on line 6. Every object in Ruby can be converted to a string using the to_s method. That’s why there is a common syntax for every type, and it’s called interpolation.

The trick is that the expression gets is evaluated inside curly braces. We have a very simple expression inside curly braces, just age_months, but it can be any Ruby code, such as 2 + 2. And at the end, the final result will get converted to a string. Let’s look at another example:

Ruby
# String Interploation Example code
puts "Your age?"
age = gets.to_i # Get age as input from user
puts "Your age is #{age * 12}" # string interpolation using curly brackets
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There are only 3 lines of code! There is no need for an extra variable, ...