Constants in classes in Ruby - Step-by-Step Execution

Concept Flow - Constants in classes

Define Class

↓

Set Constant inside Class

↓

Access Constant via Class

↓

Use Constant Value

↓

End

This flow shows how a constant is set inside a class and then accessed using the class name.

Execution Sample

Ruby

class MyClass
  MY_CONST = 10
end

puts MyClass::MY_CONST

Defines a class with a constant and prints the constant value using class scope resolution.

Execution Table

Step	Action	Code Line	State Change	Output
1	Define class MyClass	class MyClass	Class MyClass created
2	Set constant MY_CONST to 10	MY_CONST = 10	MY_CONST set to 10 inside MyClass
3	End class definition	end	Class MyClass finalized
4	Access constant MY_CONST via MyClass	puts MyClass::MY_CONST	Retrieve MY_CONST value 10	10

💡 Program ends after printing the constant value 10.

Variable Tracker

Variable	Start	After Step 2	Final
MyClass::MY_CONST	undefined	10	10

Key Moments - 2 Insights

Why do we use :: to access the constant?

The :: operator accesses constants or methods inside a class or module. Here, it tells Ruby to look inside MyClass for MY_CONST, as shown in execution_table step 4.

Can we change the value of MY_CONST after setting it?

Constants in Ruby can technically be changed but Ruby warns you. In this example, MY_CONST is set once and used as 10, as shown in variable_tracker.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of MY_CONST after step 2?

A nil

B 10

C undefined

D error

💡 Hint

Check the 'State Change' column in row for step 2 in execution_table.

At which step is the constant MY_CONST accessed to print its value?

A Step 2

B Step 3

C Step 4

D Step 1

💡 Hint

Look for the 'Action' column mentioning 'Access constant' in execution_table.

If we tried to access MY_CONST without MyClass:: prefix, what would happen?

A It would cause an error

B It would print 10

C It would print nil

D It would print 0

💡 Hint

Constants inside classes need the class name prefix to be accessed, as shown in execution_table step 4.

Concept Snapshot

class MyClass
  MY_CONST = 10  # Define constant inside class
end

Access with MyClass::MY_CONST
Constants are fixed values inside classes
Use :: to access constants inside class scope

Full Transcript

This example shows how to define a constant inside a Ruby class and access it. First, the class MyClass is created. Then, inside it, the constant MY_CONST is set to 10. After the class ends, we access the constant using MyClass::MY_CONST and print its value. Constants inside classes are accessed with the :: operator to specify the class scope. Changing constants is possible but not recommended. The program prints 10 as the output.