Raise for throwing errors in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code with raise?

Look at this Ruby code that uses raise. What will it print or return when run?

Ruby

def check_age(age)
  raise "Age must be positive" if age <= 0
  "Age is #{age}"
end

begin
  puts check_age(-1)
rescue => e
  puts e.message
end

A Age must be positive

B Age is -1

C RuntimeError: Age must be positive

D No output

💡 Hint

Think about what raise does and how rescue catches errors.

The raise command throws an error with the message "Age must be positive" because the age is -1. The rescue block catches this error and prints only the message, so the output is "Age must be positive".

🧠 Conceptual

intermediate

Which statement about raise in Ruby is true?

Choose the correct statement about how raise works in Ruby.

A <code>raise</code> only works with <code>begin</code> blocks and nowhere else.

B <code>raise</code> stops the program immediately without any chance to handle the error.

C <code>raise</code> creates an error that can be caught by <code>rescue</code> blocks.

D <code>raise</code> automatically fixes the error it detects.

💡 Hint

Think about how Ruby handles errors and exceptions.

raise creates an exception that can be caught and handled by rescue blocks. It does not stop the program immediately if handled, and it does not fix errors automatically.

🔧 Debug

advanced

Why does this Ruby code raise an error?

Look at this Ruby code. It raises an error. What is the cause?

Ruby

def divide(a, b)
  raise "Cannot divide by zero" if b == 0
  a / b
end

puts divide(10, 0)

A Because the method is missing a return statement.

B Because dividing by zero is not allowed and <code>raise</code> triggers the error.

C Because <code>raise</code> is used incorrectly without an error class.

D Because the method does not handle the error with <code>rescue</code>.

💡 Hint

Think about what happens when b is zero and how raise works.

The code raises an error because dividing by zero is not allowed. The raise command triggers a RuntimeError with the message "Cannot divide by zero" when b is zero.

📝 Syntax

advanced

Which option correctly raises a custom error in Ruby?

Choose the correct Ruby code that raises a custom error with the message "Invalid input".

A raise "Invalid input"

B raise new ArgumentError("Invalid input")

C raise ArgumentError("Invalid input")

D raise ArgumentError, "Invalid input"

💡 Hint

Remember the syntax for raising errors with a specific error class and message.

Option D uses the correct syntax: raise ArgumentError, "Invalid input". Option D raises a RuntimeError by default. Option D and D are syntax errors.

🚀 Application

expert

What is the output of this Ruby code with nested raise and rescue?

Analyze this Ruby code with nested raise and rescue. What will it print?

Ruby

def test
  begin
    raise "First error"
  rescue
    begin
      raise "Second error"
    rescue => e
      return e.message
    end
  end
end

puts test

A Second error

B RuntimeError

C No output

D First error

💡 Hint

Follow the flow of errors and rescue blocks carefully.

The first raise triggers "First error" but it is rescued immediately. Inside that rescue, another raise triggers "Second error" which is rescued and its message is returned. So the output is "Second error".