Instance_variable_get and set in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does instance_variable_get do in Ruby?

It reads the value of an instance variable from an object, even if the variable is private or not accessible by normal methods.

beginner

How do you use instance_variable_set in Ruby?

You call it on an object with the variable name (as a symbol or string starting with '@') and the new value to assign to that instance variable.

intermediate

Why might you use instance_variable_get and instance_variable_set instead of normal getters and setters?

They let you access or change instance variables directly, even if no getter or setter methods exist or if the variables are private.

beginner

What is the correct syntax to get the value of an instance variable named @name from an object obj?

obj.instance_variable_get(:@name)

beginner

What happens if you try to get an instance variable that does not exist using instance_variable_get?

It returns nil because the variable is not set on the object.

Which symbol correctly represents an instance variable named 'age' for use with instance_variable_get?

A :@age

B :age

C age

D @age

Instance variable names must start with '@' and be passed as symbols or strings, so :@age is correct.

What will obj.instance_variable_get(:@score) return if @score is not set on obj?

A An error

B 0

C nil

D false

If the instance variable does not exist, instance_variable_get returns nil.

How do you set the instance variable @level to 5 on an object player?

A player.@level = 5

B player.instance_variable_get(:@level) = 5

C player.set_instance_variable(:level, 5)

D player.instance_variable_set(:@level, 5)

Use instance_variable_set with the variable name as a symbol starting with '@' and the value.

Why might using instance_variable_get and instance_variable_set be discouraged in normal code?

A They are slower than normal methods

B They break encapsulation and can make code harder to maintain

C They only work on global variables

D They require special gems

Directly accessing instance variables bypasses encapsulation, which can lead to fragile code.

Which of these is a valid use of instance_variable_get?

A obj.instance_variable_get(:@name)

B obj.instance_variable_get('@name')

C obj.instance_variable_get('name')

D obj.instance_variable_get(:name)

The variable name must start with '@' and be passed as a symbol or string; :@name is correct.

Explain how instance_variable_get and instance_variable_set work in Ruby and when you might use them.

Think about how you can read or change private data inside an object.

Describe the risks or downsides of using instance_variable_get and instance_variable_set in your Ruby programs.

Consider how direct access to internal data affects code design.