Conditional assignment (||=) in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code using ||= operator?

Consider the following Ruby code snippet. What will be printed when it runs?

Ruby

value = nil
value ||= 10
puts value

A 0

B nil

C Error

D 10

💡 Hint

Remember ||= assigns the value only if the variable is nil or false.

The ||= operator assigns the right side value only if the left side is nil or false. Since value starts as nil, it gets assigned 10.

❓ Predict Output

intermediate

What will be the value of variable after conditional assignment?

What is the value of count after this code runs?

Ruby

count = 5
count ||= 10
puts count

A nil

B 10

C 5

D Error

💡 Hint

The ||= operator does not overwrite if the variable is already truthy.

Since count is already 5 (which is truthy), count ||= 10 does not change it.

🔧 Debug

advanced

Why does this code raise an error with ||= operator?

This Ruby code raises an error. Which option explains the cause?

Ruby

def example
  @var ||= 5
  @var = nil
  @var ||= 10
end
example

A The code runs fine and returns 10

B The code raises a SyntaxError due to misplaced ||= operator

C The second ||= is ignored because @var is nil

D Using ||= on an uninitialized instance variable causes a NameError

💡 Hint

Instance variables default to nil if uninitialized.

Instance variables in Ruby default to nil if not set. The first ||= assigns 5, then @var is set to nil, so the second ||= assigns 10. The code runs fine and returns 10.

🧠 Conceptual

advanced

What does ||= do in Ruby?

Choose the best description of what the ||= operator does in Ruby.

A Assigns the right value only if the left variable is nil or false

B Always assigns the right value to the left variable

C Assigns the right value only if the left variable is truthy

D Assigns the right value only if the left variable is zero

💡 Hint

Think about when ||= skips assignment.

The ||= operator assigns the right side value only if the left side is nil or false (i.e., falsy). Otherwise, it keeps the original value.

❓ Predict Output

expert

What is the output of this Ruby code with ||= and method calls?

What will this Ruby code print?

Ruby

def get_value
  nil
end
result = get_value ||= 100
puts result

A 100

B Error

C nil

D false

💡 Hint

Consider operator precedence and what ||= applies to here.

The expression get_value ||= 100 tries to assign to the method get_value, which is not allowed. This causes a SyntaxError.