Handling exception in Ruby

By | January 30, 2024

In Ruby, exception handling is done using the begin, rescue, else, and ensure blocks. Here’s a basic structure of a begin-rescue block:

  # Code that might raise an exception
  result = 10 / 0  # Example: Division by zero
rescue ExceptionType => e
  # Handle the exception
  puts "An exception of type #{e.class} occurred: #{e.message}"
  # Code to be executed if no exception occurs
  puts "No exception occurred."
  # Code that will be executed no matter what
  puts "This code will always run."

Let’s break down the components:

  • The begin block contains the code that might raise an exception.
  • The rescue block catches and handles the exception. You can catch specific exception types or a general Exception type.
  • The else block contains code that will be executed if no exception occurs.
  • The ensure block contains code that will be executed no matter what, whether an exception occurred or not.

Example with a specific exception:

  print "Enter a number: "
  num = gets.chomp.to_i
  result = 10 / num
rescue ZeroDivisionError
  puts "Cannot divide by zero."
rescue => e
  puts "An unexpected error occurred: #{e.message}"
  puts "Result: #{result}"
  puts "Execution completed."

In this example:

  • If the user enters 0, a ZeroDivisionError is caught.
  • If the user enters a non-numeric value, the general rescue block catches the exception.
  • If the user enters a valid number, the result is displayed in the else block.
  • The ensure block ensures that the final message is printed regardless of the outcome.

As with any language, it’s good practice to catch only the exceptions you expect and handle them appropriately. Avoid catching overly broad exceptions unless necessary.

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