Attr_reader, attr_writer, attr_accessor in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a read-only attribute for :name.

Ruby

class Person
  [1] :name
end

Drag options to blanks, or click blank then click option'

Aattr_writer

Battr_reader

Cattr_accessor

Dattr_private

Attempts:

3 left

💡 Hint

Common Mistakes

Using attr_writer instead of attr_reader will create write-only attribute.

Using attr_accessor creates both getter and setter.

Use attr_reader to create a read-only attribute.

2fill in blank

medium

Complete the code to create a write-only attribute for :password.

Ruby

class User
  [1] :password
end

Drag options to blanks, or click blank then click option'

Aattr_writer

Battr_reader

Cattr_accessor

Dattr_private

Attempts:

3 left

💡 Hint

Common Mistakes

Using attr_reader will create read-only attribute, not write-only.

attr_accessor creates both getter and setter.

Use attr_writer to create a write-only attribute.

3fill in blank

hard

Fix the error in the code to allow reading and writing for :email.

Ruby

class Contact
  [1] :email
end

Drag options to blanks, or click blank then click option'

Aattr_reader

Battr_writer

Cattr_private

Dattr_accessor

Attempts:

3 left

💡 Hint

Common Mistakes

Using attr_reader or attr_writer alone will not allow both reading and writing.

attr_accessor creates both getter and setter methods.

4fill in blank

hard

Fill both blanks to create a class with read-only :title and write-only :secret attributes.

Ruby

class Document
  [1] :title
  [2] :secret
end

Drag options to blanks, or click blank then click option'

Aattr_reader

Battr_writer

Cattr_accessor

Dattr_private

Attempts:

3 left

💡 Hint

Common Mistakes

Using attr_accessor for both will allow both reading and writing.

Mixing up attr_reader and attr_writer.

attr_reader for read-only :title and attr_writer for write-only :secret.

5fill in blank

hard

Fill all three blanks to create a class with read-write :name, read-only :age, and write-only :password.

Ruby

class Account
  [1] :name
  [2] :age
  [3] :password
end

Drag options to blanks, or click blank then click option'

Aattr_reader

Battr_writer

Cattr_accessor

Dattr_private

Attempts:

3 left

💡 Hint

Common Mistakes

Using attr_reader or attr_writer incorrectly for attributes needing both read and write.

Using attr_private which is not a valid Ruby method.

attr_accessor for read-write :name, attr_reader for read-only :age, and attr_writer for write-only :password.

Practice

1. What does attr_reader do in a Ruby class?

easy

A. Creates a method to read an attribute value

B. Creates a method to write an attribute value

C. Creates methods to both read and write an attribute

D. Deletes an attribute from the class

Solution

1. Step 1: Understand attr_reader purpose

   attr_reader defines a getter method for an instance variable, allowing you to read its value.

2. Step 2: Compare with other attr methods

   attr_writer creates a setter (write) method, and attr_accessor creates both getter and setter methods.

3. Final Answer:

   Creates a method to read an attribute value -> Option A

4. Quick Check:

   attr_reader = read method [OK]

Hint: attr_reader = read only method [OK]

Common Mistakes:

• Confusing attr_reader with attr_writer
• Thinking attr_reader allows writing values
• Mixing attr_accessor with attr_reader

2. Which of the following is the correct syntax to create both getter and setter methods for @name in Ruby?

easy

A. attr_writer :name

B. attr_accessor :name

C. attr_reader :name

D. attr_both :name

Solution

1. Step 1: Recall attr_accessor usage

   attr_accessor creates both getter and setter methods for the given symbol.

2. Step 2: Check other options

   attr_reader only creates getter, attr_writer only setter, and attr_both is invalid syntax.

3. Final Answer:

   attr_accessor :name -> Option B

4. Quick Check:

   attr_accessor = read + write [OK]

Hint: Use attr_accessor for read and write [OK]

Common Mistakes:

• Using attr_reader when write is needed
• Using invalid method names like attr_both
• Confusing attr_writer with attr_accessor

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

class Person
  attr_writer :age
  def initialize(age)
    @age = age
  end
  def show_age
    @age
  end
end

p = Person.new(30)
puts p.show_age
p.age = 40
puts p.show_age

medium

A. 30\n40

B. 30\n30

C. Error: undefined method `age='

D. Error: undefined method `show_age'

Solution

1. Step 1: Understand attr_writer effect

   attr_writer :age creates a setter method age=, but no getter method is created.

2. Step 2: Analyze method calls

   p.show_age returns @age which is 30 initially. Then p.age = 40 sets @age to 40. But p.show_age returns @age which is now 40.

3. Step 3: Check output

   Actually, p.show_age is called twice, before and after setting age. So outputs are 30 then 40.

4. Final Answer:

   30\n40 -> Option A

5. Quick Check:

   attr_writer allows setting, show_age reads @age [OK]

Hint: attr_writer only sets; custom getter needed [OK]

Common Mistakes:

• Assuming attr_writer creates getter method
• Expecting error on p.age= assignment
• Confusing show_age method with attr_reader

4. Identify the error in this Ruby class:

class Car
  attr_reader :model
  def initialize(model)
    @model = model
  end
  def model=(value)
    @model = value
  end
end

car = Car.new('Sedan')
car.model = 'SUV'
puts car.model

medium

A. Error: attr_reader conflicts with manual setter method

B. Error: undefined method 'model='

C. Error: attr_reader does not create setter method

D. No error, code runs and prints 'SUV'

Solution

1. Step 1: Check attr_reader and setter method

   attr_reader :model creates a getter method. The setter method model= is manually defined.

2. Step 2: Analyze method calls

   car.model = 'SUV' calls the manual setter, updating @model. puts car.model calls the getter from attr_reader, printing 'SUV'.

3. Final Answer:

   No error, code runs and prints 'SUV' -> Option D

4. Quick Check:

   attr_reader + manual setter works [OK]

Hint: attr_reader + manual setter is valid [OK]

Common Mistakes:

• Assuming attr_reader creates setter method
• Thinking attr_reader conflicts with manual setter
• Expecting error on model= assignment

5. You want a Ruby class Book where the title can be read but not changed, and the author can be both read and changed. Which attribute methods should you use?

hard

A. attr_writer :title
attr_writer :author

B. attr_writer :title
attr_reader :author

C. attr_reader :title
attr_accessor :author

D. attr_accessor :title
attr_writer :author

Solution

1. Step 1: Determine access for title

   Title should be readable but not writable, so use attr_reader :title.

2. Step 2: Determine access for author

   Author should be readable and writable, so use attr_accessor :author.

3. Final Answer:

   attr_reader :title attr_accessor :author -> Option C

4. Quick Check:

   Read-only + read-write = attr_reader + attr_accessor [OK]

Hint: Use attr_reader for read-only, attr_accessor for read-write [OK]

Common Mistakes:

• Using attr_writer for read-only attribute
• Using attr_accessor for read-only attribute
• Mixing up read and write access