Method naming conventions (? and ! suffixes) in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does a method name ending with a ? usually indicate in Ruby?

It indicates that the method returns a boolean value (true or false), often used for predicate methods that ask a question about an object.

beginner

What is the purpose of a method name ending with a ! in Ruby?

It signals that the method is "dangerous" or performs its action in a more surprising or destructive way, often modifying the object in place.

intermediate

Can a method have both ? and ! suffixes in Ruby?

No, Ruby does not allow method names to end with both ? and ! at the same time.

beginner

Why should you use ? suffix only for methods that return boolean values?

Because it helps other programmers understand that the method answers a yes/no question, improving code readability and intention clarity.

intermediate

Give an example of a Ruby method with a ! suffix and explain its behavior.

Example: upcase! modifies the string in place to uppercase letters, unlike upcase which returns a new string without changing the original.

What does a Ruby method ending with ? usually return?

A A boolean value (true or false)

B A modified object

C An error message

D A string

Methods ending with ? are predicate methods that return true or false.

What does the ! suffix in a Ruby method name usually warn about?

A The method is slow

B The method modifies the object or is dangerous

C The method returns a boolean

D The method is deprecated

The ! suffix warns that the method may change the object or behave in a surprising way.

Which of these is a valid Ruby method name?

A dangerous_method!

B valid_method?

C check_method?!

D method!?

Methods can end with either ? or !, but not both or in combination.

Why is it important to follow the ? and ! naming conventions in Ruby?

A To make code run faster

B To make methods private

C To improve code readability and communicate method behavior

D To avoid syntax errors

These suffixes help programmers understand what the method does at a glance.

What does the method empty? typically check in Ruby?

A If a number is zero

B If an object is nil

C If a method is dangerous

D If a collection or string has no elements or characters

empty? returns true if a string or collection has no content.

Explain the difference between Ruby methods ending with ? and those ending with !.

Think about how these suffixes help communicate what the method does.

Why is it helpful to use ? and ! suffixes in method names when writing Ruby code?

Consider how naming conventions affect teamwork and maintenance.

Practice

1. Which method name follows Ruby convention for a method that returns a boolean value?
? is used at the end of method names that return true or false.

easy

A. save

B. update!

C. calculate

D. valid?

Solution

1. Step 1: Understand the meaning of ? suffix

   In Ruby, methods ending with ? return true or false, indicating a boolean check.

2. Step 2: Identify the method that returns a boolean

   Among the options, valid? clearly suggests a boolean check, while others do not.

3. Final Answer:

   valid? -> Option D

4. Quick Check:

   Boolean methods end with ? = valid? [OK]

Hint: Boolean methods end with ? to show true/false result [OK]

Common Mistakes:

• Confusing ! with ? suffix
• Using ? for methods that modify objects
• Not using ? for boolean-returning methods

2. Which of the following method names is correctly written to indicate it modifies the object in Ruby?

easy

A. delete

B. delete!

C. delete?

D. deleted

Solution

1. Step 1: Understand the meaning of ! suffix

   In Ruby, methods ending with ! usually modify the object or perform a 'dangerous' action.

2. Step 2: Identify the method that modifies the object

   delete! clearly indicates modification, while delete may not, and delete? suggests a boolean check.

3. Final Answer:

   delete! -> Option B

4. Quick Check:

   Modification methods end with ! = delete! [OK]

Hint: Use ! for methods that change the object [OK]

Common Mistakes:

• Using ? instead of ! for modifying methods
• Not adding ! for dangerous methods
• Confusing method names without suffixes

3. What will be the output of this Ruby code?

class User
  def active?
    true
  end

  def deactivate!
    @active = false
    "User deactivated"
  end
end

user = User.new
puts user.active?
puts user.deactivate!
puts user.active?

medium

A. true
User deactivated
true

B. true
User deactivated
false

C. false
User deactivated
false

D. true
User deactivated
nil

Solution

1. Step 1: Analyze the active? method

   This method always returns true because it returns the literal true without checking any variable.

2. Step 2: Analyze the deactivate! method and second active? call

   deactivate! sets @active = false but active? does not use @active, so it still returns true.

3. Final Answer:

   true User deactivated true -> Option A

4. Quick Check:

   active? returns true always = true User deactivated true [OK]

Hint: Check if boolean method uses instance variables or fixed return [OK]

Common Mistakes:

• Assuming deactivate! changes active? output
• Confusing method side effects
• Ignoring method return values

4. Identify the error in this Ruby method definition:

def save?
  # saves the object
  puts "Saving..."
  true
end

What is wrong with this method name?

medium

A. Method name cannot contain ?

B. Method should end with ! instead of ?

C. Method ends with ? but performs an action, not a boolean check

D. No error, method is correct

Solution

1. Step 1: Understand the meaning of ? suffix

   Methods ending with ? should return true or false and not perform side effects like saving.

2. Step 2: Analyze the method behavior

   This method prints "Saving..." which is a side effect, so it should not end with ?.

3. Final Answer:

   Method ends with ? but performs an action, not a boolean check -> Option C

4. Quick Check:

   Methods with ? should not have side effects [OK]

Hint: ? means boolean check, not side effects [OK]

Common Mistakes:

• Using ? for methods that change state
• Ignoring method side effects
• Confusing ! and ? suffix meanings

5. You want to write a Ruby method that checks if a string is empty and also a method that clears the string content. Which method names follow Ruby conventions?

hard

A. empty? and clear!

B. empty! and clear?

C. empty and clear!

D. empty? and clear

Solution

1. Step 1: Identify boolean check method

   The method checking if a string is empty should return true or false, so it should end with ?, e.g., empty?.

2. Step 2: Identify modifying method

   The method that clears the string modifies it, so it should end with !, e.g., clear!.

3. Final Answer:

   empty? and clear! -> Option A

4. Quick Check:

   Boolean check ends with ?; modifying method ends with ! [OK]

Hint: Boolean methods end with ?; modifying methods end with ! [OK]

Common Mistakes:

• Swapping ? and ! suffixes
• Not using suffixes for clarity
• Using no suffix for modifying methods