Variables

A variable is a label that Ruby assigns to a particular object. There are four different types of variables in Ruby. Each type starts with a special character to indicate the type of variable it is.

Local Variables

Local variables must begin with a lowercase letter or _ . These variables are local to the code block of the method they are declared in.

color = "green" 
_person = "Shannon" 
 
There is nothing special about the word color in this line of code. It’s just a variable name. You could set pizza = "green" . While that variable name choice might be misleading to the human reading it, the value would still be "green" .
Instance Variables
Instance variables begin with an @ symbol. Instance variables are variables that belong to an object.
class Person 
 
def initialize(first, middle, last) 
 
# Instance Variables 
 
@first_name = first
 
@middle_name = middle
 
@last_name = last
 
end 
 
# Displaying result 
 
def display_full_name() 
 puts "Full name: #@first_name #@middle_name #@last_name" 
 
end 
 
end 
 
# Create Objects 
person1 = Person.new("Alexandra", "Smith", "Johnson") 
person2 = Person.new("Marcus", "Alonzo", "Thomas") 
 
# Call Methods 
person1.display_full_name() 
person2.display_full_name() 
 
# Output: Full name: Alexandra Smith Johnson 
 
# Output: Full name: Marcus Alonzo Thomas 
 
Class Variables
Class variables begin with an @@ sign. Class variables are available across different objects shared by all the descendants of the class. They must be initialized before use.
class Person 
 
# Class variable 
 
@@number_of_people = 0 
 
def initialize(first, middle, last) 
 
@first_name = first
 
@middle_name = middle
 
@last_name = last
 
end 
 
# displaying result 
 
def display_full_name() 
 puts "Full name: #@first_name #@middle_name #@last_name" 
 
end 
 
def total_no_of_people() 
 
# class variable 
 
@@number_of_people += 1 
 puts "Total number of people: #@@number_of_people" 
 
end 
 
end 
 
# Create Objects 
person1 = Person.new("Alexandra", "Smith", "Johnson") 
person2 = Person.new("Marcus", "Alonzo", "Thomas") 
 
# Call Methods 
person1.display_full_name() 
person1.total_no_of_people() 
person2.display_full_name() 
person2.total_no_of_people() 
 
# Output: Full name: Alexandra Smith Johnson 
 
# Output: Total number of people: 1 
 
# Output: Full name: Marcus Alonzo Thomas 
 
# Output: Total number of people: 2 
 
Global Variables
Global variables begin with an $ symbol. While Class variables are not available across different classes, global variables are. Its scope is global, meaning that it can be accessed from anywhere in the program.
# Global variable 
 
$global_variable_starting_score = 0 
 
class Class1 
 
def print_global_starting_score 
 
# Access global variable 
 puts "The starting score in Class1 is #$global_variable_starting_score" 
 
end 
 
end 
 
class Class2 
 
def print_global_starting_score 
 
# Access global variable 
 puts "The starting score in Class2 is #$global_variable_starting_score" 
 
end 
 
end 
 
class1obj = Class1.new 
class1obj.print_global_starting_score
class2obj = Class2.new 
class2obj.print_global_starting_score
 
# Output: The starting score in Class1 is 0 
 
# Output: The starting score in Class2 is 0