Multiple rescue clauses in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of multiple rescue clauses with different exceptions

What is the output of this Ruby code with multiple rescue clauses?

Ruby

begin
  1 / 0
rescue ZeroDivisionError
  puts "ZeroDivisionError caught"
rescue StandardError
  puts "StandardError caught"
end

A StandardError caught

B ZeroDivisionError caught

C No output, program crashes

D RuntimeError caught

💡 Hint

Think about which error is raised by dividing by zero in Ruby.

Dividing by zero raises a ZeroDivisionError, so the first rescue clause matches and prints "ZeroDivisionError caught".

❓ Predict Output

intermediate

Which rescue clause handles the exception?

What will this Ruby code print?

Ruby

begin
  [].fetch(10)
rescue IndexError
  puts "IndexError handled"
rescue KeyError
  puts "KeyError handled"
end

A KeyError handled

B ArgumentError handled

C No output, program crashes

D IndexError handled

💡 Hint

Check what exception is raised when fetching an invalid index from an array.

Calling fetch with an invalid index raises IndexError, so the first rescue clause runs.

❓ Predict Output

advanced

Output when multiple exceptions are rescued with one clause

What does this Ruby code output?

Ruby

begin
  {}.fetch(:foo)
rescue KeyError, NoMethodError
  puts "KeyError or NoMethodError rescued"
rescue StandardError
  puts "StandardError rescued"
end

A KeyError or NoMethodError rescued

B StandardError rescued

C No output, program crashes

D TypeError rescued

💡 Hint

Accessing a missing key in a hash with [] returns nil, but with fetch it raises KeyError.

Hash#fetch raises KeyError for missing keys, so the first rescue clause matches and prints "KeyError or NoMethodError rescued".

❓ Predict Output

advanced

Which rescue clause runs with nested exceptions?

What will this Ruby code print?

Ruby

begin
  begin
    raise ArgumentError, "wrong argument"
  rescue TypeError
    puts "TypeError rescued"
  end
rescue ArgumentError
  puts "ArgumentError rescued"
end

A No output, program crashes

B TypeError rescued

C ArgumentError rescued

D RuntimeError rescued

💡 Hint

The inner rescue only catches TypeError, but the raised error is ArgumentError.

The inner rescue does not catch ArgumentError, so it propagates to the outer rescue which catches ArgumentError and prints "ArgumentError rescued".

❓ Predict Output

expert

Output of multiple rescue clauses with else and ensure

What is the output of this Ruby code?

Ruby

begin
  puts "Start"
  10 / 2
rescue ZeroDivisionError
  puts "ZeroDivisionError caught"
rescue StandardError
  puts "StandardError caught"
else
  puts "No errors"
ensure
  puts "Always runs"
end

A

Start
No errors
Always runs

B

Start
ZeroDivisionError caught
Always runs

C

Start
Always runs

D

Start
StandardError caught
Always runs

💡 Hint

The else clause runs only if no exception is raised.

The division 10 / 2 does not raise an error, so the else clause runs printing "No errors". The ensure clause always runs printing "Always runs".