Exception hierarchy in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of exception class inheritance check

What is the output of this Ruby code snippet?

Ruby

puts ZeroDivisionError < StandardError
puts StandardError < Exception
puts Exception < Object

A

true
true
true

B

false
true
true

C

true
false
true

D

true
true
false

💡 Hint

Remember that ZeroDivisionError inherits from StandardError, which inherits from Exception, which inherits from Object.

In Ruby, ZeroDivisionError is a subclass of StandardError, which is a subclass of Exception, and Exception inherits from Object. The < operator checks if the left class is a subclass of the right class.

❓ Predict Output

intermediate

Exception rescue specificity

What will be printed when this Ruby code runs?

Ruby

begin
  raise IOError, 'file error'
rescue StandardError
  puts 'rescued StandardError'
rescue IOError
  puts 'rescued IOError'
end

A rescued IOError

B rescued StandardError

C no output

D RuntimeError

💡 Hint

Consider the order of rescue clauses and inheritance of IOError.

In Ruby, IOError inherits from StandardError. The first rescue clause that matches the exception type is executed. Since rescue StandardError comes before rescue IOError, it catches the IOError first.

🔧 Debug

advanced

Identify the error type raised

What error type will this Ruby code raise when executed?

Ruby

begin
  1 / 0
rescue => e
  puts e.class
end

A ArgumentError

B TypeError

C NoMethodError

D ZeroDivisionError

💡 Hint

Dividing by zero in Ruby raises a specific error.

Dividing an integer by zero in Ruby raises a ZeroDivisionError. The rescue block captures the exception and prints its class.

❓ Predict Output

advanced

Custom exception inheritance check

Given this Ruby code, what is the output?

Ruby

class MyError < StandardError; end
class MySubError < MyError; end

puts MySubError < StandardError
puts MyError < Exception
puts MySubError < Exception

A

true
true
true

B

true
false
true

C

true
true
false

D

false
true
false

💡 Hint

Trace the inheritance chain from subclasses to their ancestors.

Both MyError and MySubError inherit from StandardError, which inherits from Exception. The < operator returns true if the left class is a subclass of the right class.

🧠 Conceptual

expert

Understanding Ruby exception hierarchy root

Which class is the root of all exception classes in Ruby?

A Object

B StandardError

C Exception

D RuntimeError

💡 Hint

Think about which class all exceptions inherit from directly or indirectly.

In Ruby, Exception is the root class for all exceptions. StandardError and other error classes inherit from Exception. Object is the root of all Ruby objects but not specifically exceptions.