How to Use begin rescue in Ruby for Error Handling

In Ruby, use begin and rescue to handle errors by wrapping code that might fail inside begin and catching exceptions with rescue. This lets your program continue running even if an error occurs.

Syntax

The begin block contains code that might raise an error. The rescue block catches and handles the error. You can also use else for code that runs if no error happens, and ensure for code that always runs.

• begin: Start of the block that may raise an error.
• rescue: Handles exceptions raised in the begin block.
• else: Runs if no exceptions occur.
• ensure: Runs always, whether an error occurred or not.

ruby

begin
  # code that might raise an error
rescue SomeErrorClass => e
  # code to handle the error
else
  # code that runs if no error
ensure
  # code that always runs
end

Example

This example shows how begin and rescue catch a division by zero error and handle it gracefully.

ruby

begin
  puts "Enter a number to divide 10 by:"
  number = gets.chomp.to_i
  result = 10 / number
  puts "Result is #{result}"
rescue ZeroDivisionError => e
  puts "Error: Cannot divide by zero!"
end

Output

Enter a number to divide 10 by:
0
Error: Cannot divide by zero!

Common Pitfalls

One common mistake is rescuing Exception which catches too many errors, including system errors you usually don't want to handle. Another is rescuing without specifying the error type, which can hide bugs. Also, forgetting to use rescue inside begin causes unhandled exceptions.

ruby

begin
  # risky code
rescue
  puts "An error happened"
end

# Better to specify error type:
begin
  # risky code
rescue ZeroDivisionError => e
  puts "Handled division error: #{e.message}"
end

Quick Reference

Keyword	Purpose
begin	Start block of code that might raise errors
rescue	Catch and handle specific errors
else	Run code if no errors occur
ensure	Run code always, even if error occurs

Key Takeaways

Use begin and rescue to catch and handle errors in Ruby.

Always specify the error type in rescue to avoid hiding bugs.

Use else for code that runs only if no error occurs.

Use ensure for code that must run regardless of errors.

Avoid rescuing Exception to prevent catching system errors unintentionally.