Guard clauses pattern in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of method using guard clauses

What is the output of this Ruby method when called with the argument 5?

Ruby

def check_number(num)
  return "Too small" if num < 3
  return "Too large" if num > 10
  "Just right"
end

puts check_number(5)

A Just right

B Too large

C Too small

D nil

💡 Hint

Look at the conditions and see which guard clause applies for 5.

The method returns early if the number is less than 3 or greater than 10. Since 5 is between 3 and 10, it reaches the last line returning "Just right".

❓ Predict Output

intermediate

Return value with multiple guard clauses

What will this Ruby method return when called with the argument 0?

Ruby

def status_code(code)
  return "Error" if code < 0
  return "Success" if code == 0
  "Unknown"
end

puts status_code(0)

A Error

B Unknown

C Success

D nil

💡 Hint

Check which guard clause matches the input 0.

The method returns "Success" immediately if the code equals 0, so it does not reach the last line.

🔧 Debug

advanced

Identify the error in guard clause usage

What error will this Ruby code raise when executed?

Ruby

def process(value)
  return "No value" unless value
  return "Zero" if value == 0
  value * 2
end

puts process(nil)

A NoMethodError

B TypeError

C ArgumentError

D No error, outputs "No value"

💡 Hint

Check the guard clause with 'unless value' and what happens with nil.

The guard clause returns "No value" immediately if value is nil (which is falsey), so no error occurs.

❓ Predict Output

advanced

Output of method with nested guard clauses

What is the output of this Ruby method when called with argument 15?

Ruby

def evaluate(num)
  return "Negative" if num < 0
  return "Small" if num < 10
  return "Medium" if num < 20
  "Large"
end

puts evaluate(15)

A Medium

B Negative

C Small

D Large

💡 Hint

Check each guard clause in order for 15.

15 is not less than 0 or 10, but it is less than 20, so the method returns "Medium".

❓ Predict Output

expert

Return value with complex guard clauses and side effects

What will be printed when this Ruby code runs?

Ruby

def complex_check(x)
  return "Negative" if x < 0
  puts "Checking zero"
  return "Zero" if x == 0
  return "Positive" if x > 0
  "Unknown"
end

result = complex_check(0)
puts result

A

Negative
Negative

B

Checking zero
Zero

C

Zero
Zero

D

Checking zero
Positive

💡 Hint

Notice the puts inside the method before the guard clause for zero.

When x is 0, the method prints "Checking zero" then returns "Zero", so the output is two lines: first the printed string, then the returned string printed outside.