Ensure for cleanup in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the ensure block in Ruby?

The ensure block runs code that must execute no matter what happens in the begin block, such as cleaning up resources or closing files.

beginner

How does ensure differ from rescue in Ruby?

rescue handles exceptions when they occur, while ensure always runs after begin, whether an exception happened or not.

intermediate

What happens if an exception is raised inside an ensure block?

If an exception occurs inside ensure, it will override any previous exception and propagate up, potentially hiding the original error.

beginner

Why is ensure useful for resource cleanup?

ensure guarantees that cleanup code like closing files or releasing locks runs even if an error interrupts normal flow.

beginner

Example: What will this Ruby code print?

begin
  puts 'Start'
  raise 'Oops'
rescue
  puts 'Rescued'
ensure
  puts 'Always runs'
end

It prints:<br>Start<br>Rescued<br>Always runs<br>The ensure block runs last no matter what.

What does the ensure block guarantee in Ruby?

A Code inside it runs before the <code>begin</code> block

B Code inside it runs only if no exception occurs

C Code inside it runs only if an exception occurs

D Code inside it always runs, even if an exception occurs

The ensure block always runs after begin, regardless of exceptions.

Which block handles exceptions in Ruby?

A <code>begin</code>

B <code>ensure</code>

C <code>rescue</code>

D <code>finally</code>

rescue handles exceptions; ensure runs cleanup code.

If an exception is raised in ensure, what happens?

A It replaces any previous exception

B The program exits silently

C It is caught by <code>rescue</code>

D It is ignored

Exceptions in ensure override previous exceptions and propagate.

Where should you put code to close a file to ensure it always runs?

A Inside <code>begin</code>

B Inside <code>ensure</code>

C Inside <code>rescue</code>

D Outside all blocks

Closing files should be in ensure to guarantee execution.

What will this code print?

begin
  puts 'Hello'
ensure
  puts 'Goodbye'
end

A Hello Goodbye

B Goodbye

C Hello

D Goodbye Hello

Both puts run; ensure runs after begin.

Explain how the ensure block works in Ruby and why it is important for cleanup.

Think about what happens when errors occur and you still want to clean up.

Describe the difference between rescue and ensure blocks in Ruby exception handling.

One catches errors, the other guarantees code runs.