Constants in classes in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a constant in a Ruby class?

A constant in a Ruby class is a value that is meant to stay the same throughout the program. It is written with a name starting with a capital letter and usually holds data that should not change.

beginner

How do you define a constant inside a Ruby class?

You define a constant inside a Ruby class by writing the constant name starting with a capital letter, followed by an equal sign and the value. For example: <pre>class MyClass
  MY_CONSTANT = 10
end</pre>

intermediate

Can you change the value of a constant in Ruby after it is set?

Technically, you can change a constant's value in Ruby, but it will give a warning because constants are meant to stay the same. Changing them is not recommended.

beginner

How do you access a constant defined inside a Ruby class from outside the class?

You access a constant from outside the class by using the scope resolution operator :: with the class name. For example: <pre>MyClass::MY_CONSTANT</pre>

intermediate

What happens if you define a constant with the same name in a subclass in Ruby?

If a subclass defines a constant with the same name as in its parent class, the subclass's constant will override the parent's constant when accessed from the subclass.

How do you write a constant name in Ruby?

A Starts with a lowercase letter

B Starts with a number

C Starts with an underscore

D Starts with a capital letter

In Ruby, constants must start with a capital letter.

How do you access a constant MY_CONST inside class MyClass from outside?

A MyClass::MY_CONST

B MyClass.MY_CONST

C MyClass->MY_CONST

D MY_CONST.MyClass

Use the scope resolution operator :: to access constants inside classes.

What happens if you change a constant's value in Ruby?

A Ruby deletes the constant

B Ruby throws an error and stops

C Ruby allows it but shows a warning

D Ruby ignores the change silently

Ruby allows changing constants but warns you because it's not recommended.

Where should constants be defined in Ruby?

A Only inside methods

B Inside classes or modules

C Only in global scope

D Inside local variables

Constants are usually defined inside classes or modules to organize them.

If a subclass defines a constant with the same name as its parent, which one is used inside the subclass?

A The subclass's constant

B The parent's constant

C Both constants are merged

D An error occurs

The subclass's constant overrides the parent's constant when accessed from the subclass.

Explain how to define and access constants inside Ruby classes.

Think about how you write constants and how you get their values from outside.

Describe what happens when you try to change a constant's value in Ruby and why it matters.

Consider Ruby's behavior and why constants exist.