Method naming conventions (? and ! suffixes) in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code with a method ending with '?'?

Consider the following Ruby code. What will be printed when calling even_number??

Ruby

def even_number?(num)
  num % 2 == 0
end

puts even_number?(4)
puts even_number?(5)

A nil\nnil

B false\ntrue

C 4\n5

D true\nfalse

💡 Hint

Methods ending with '?' usually return true or false.

The method even_number? checks if a number is even and returns a boolean. For 4, it returns true; for 5, false.

❓ Predict Output

intermediate

What does the method ending with '!' do differently?

Look at this Ruby code. What will be the output after calling capitalize! on the string?

Ruby

str = "hello"
result = str.capitalize!
puts str
puts result

A hello\nHello

B Hello\nHello

C Hello\nhello

D hello\nhello

💡 Hint

Methods ending with '!' usually modify the object itself.

The capitalize! method changes the original string to "Hello" and returns the modified string.

🔧 Debug

advanced

Why does this method with '?' suffix raise an error?

This Ruby method is intended to check if a number is positive. Why does it raise a syntax error?

Ruby

def positive?(num)
  if num > 0
    return true
  else
    return false
  end
end

A Because the 'end' keyword is followed by an extra '?', which is invalid syntax.

B Because method names cannot end with '?' and have an extra '?' after 'end'.

C Because 'return' cannot be used inside methods ending with '?'.

D Because the method is missing a closing parenthesis.

💡 Hint

Check the syntax after the method body ends.

The extra '?' after the 'end' keyword is invalid syntax in Ruby, causing a syntax error.

❓ Predict Output

advanced

What is the output of this code using both '?' and '!' methods?

Given this Ruby code, what will be printed?

Ruby

class User
  attr_accessor :name

  def initialize(name)
    @name = name
  end

  def name?
    !@name.nil? && !@name.empty?
  end

  def clear_name!
    @name = ""
  end
end

user = User.new("Alice")
puts user.name?
user.clear_name!
puts user.name?

A true\ntrue

B false\ntrue

C true\nfalse

D false\nfalse

💡 Hint

The '?' method checks if name is present; the '!' method clears it.

Initially, name is "Alice", so name? returns true. After clearing, name is empty string, so name? returns false.

🧠 Conceptual

expert

Why should methods ending with '!' be used carefully in Ruby?

Which of the following best explains the purpose and caution behind methods ending with '!' in Ruby?

A They indicate methods that modify the object in place and may have side effects, so use them only when you want to change the original object.

B They are methods that always return true or false and should be used for checks only.

C They are methods that raise exceptions on failure and never modify the object.

D They are deprecated methods and should be avoided in modern Ruby code.

💡 Hint

Think about what the '!' means in method names in Ruby conventions.

In Ruby, methods ending with '!' usually modify the object they are called on and may have side effects, so they should be used carefully.