Begin/rescue/end blocks in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple rescue block

What is the output of this Ruby code?

Ruby

def test
  begin
    1 / 0
  rescue ZeroDivisionError
    "divided by zero"
  end
end

puts test

A ZeroDivisionError

B divided by zero

C 0

D Infinity

💡 Hint

Look at what happens when dividing by zero inside the begin block and how rescue handles it.

The division by zero raises a ZeroDivisionError, which is caught by the rescue block. The rescue block returns the string "divided by zero", which is then printed.

❓ Predict Output

intermediate

Return value with ensure block

What will this Ruby code print?

Ruby

def example
  begin
    return 1
  ensure
    puts "ensure block"
  end
end

puts example

A 1

B ensure block

C

ensure block
1

D

1
ensure block

💡 Hint

Remember that ensure runs even if there is a return inside begin.

The method returns 1, but before returning, the ensure block runs and prints "ensure block". Then the returned value 1 is printed by puts.

🔧 Debug

advanced

Identify the error in rescue syntax

Which option contains a syntax error in the rescue block?

Ruby

begin
  puts 10 / 0
rescue ZeroDivisionError => e
  puts e.message
end

A

begin
  puts 10 / 0
rescue ZeroDivisionError => e
  puts e.message
end

B

begin
  puts 10 / 0
rescue ZeroDivisionError, NameError => e
  puts e.message
end

C

begin
  puts 10 / 0
rescue ZeroDivisionError
  puts 'error'
end

D

begin
  puts 10 / 0
rescue => e ZeroDivisionError
  puts e.message
end

💡 Hint

Check the placement of the exception class and variable in rescue syntax.

Option D places the exception variable 'e' before the exception class, which is invalid syntax. The correct syntax is 'rescue ExceptionClass => variable'.

🧠 Conceptual

advanced

Behavior of nested begin/rescue blocks

What will be the output of this Ruby code?

Ruby

begin
  begin
    raise "error"
  rescue RuntimeError
    puts "inner rescue"
    raise
  end
rescue
  puts "outer rescue"
end

A

inner rescue
outer rescue

B

outer rescue
inner rescue

C inner rescue

D outer rescue

💡 Hint

Consider how the inner rescue handles the error and what happens when it re-raises it.

The inner rescue catches the RuntimeError and prints "inner rescue". Then it re-raises the error, which is caught by the outer rescue that prints "outer rescue".

❓ Predict Output

expert

Output with multiple rescue clauses and ensure

What is the output of this Ruby code?

Ruby

def test
  begin
    raise ArgumentError, "wrong argument"
  rescue ZeroDivisionError
    puts "zero division"
  rescue ArgumentError => e
    puts e.message
  ensure
    puts "always runs"
  end
end

test

A

wrong argument
always runs

B

zero division
always runs

C

always runs
wrong argument

D

ArgumentError
always runs

💡 Hint

Check which rescue clause matches the raised exception and the order of ensure execution.

The raised ArgumentError matches the second rescue clause, printing its message "wrong argument". The ensure block always runs, printing "always runs" after.