Variables in ruby Variables are used to hold any data which will be later used by programs. There are 5 types of variables in ruby

1.Ruby global variables

2.Ruby instance variables

3.Ruby class varibles

4.Ruby local variable

5.Ruby Constants

I will explain in detail about each variable Ruby global variable are used globally in whole application. Ruby global variable are denoted by $ sign

       $global_variable = 10
    class Demo
      def show_global
         puts "Global variable in Demo1 is #$global_variable"
      end
    end
    class Demo2
      def show_global
         puts "Global variable in Demo2 is #$global_variable"
      end
    end

    obj1 = Demo.new
    obj1.show_global
    obj2 = Demo2.new
    obj2.show_global

   Output:-
   Global variable in Demo1 is 10
    => nil 
   Global variable in Demo2 is 10

   

Instance variable:-

Instance variable are denoted by @. uninitialized instance variable produce nil value.

  class Customer
       def initialize(id)
          @cust_id=id
       end
       def display_details
          puts "Customer id #@cust_id"
        end
    end

    # Create Objects
    cust1=Customer.new("1")
    cust2=Customer.new("2")

    # Call Methods
    cust1.display_details
    cust2.display_details

  

      Output:-
      Customer id 1
        => nil    
      Customer id 2
        => nil 
  

here @cust_id is instance variable Ruby class variable\ Class variables are used by the @@ and must be initialized before using in class

class People
   @@no_of_people=0
   def initialize(id, name, addr)
      @cust_id=id
      @cust_name=name
      @cust_addr=addr
   end
   def display_details
      puts "Customer id #@custe @@no_of_customers in People
_id"
      puts "Customer name #@cust_name"
      puts "Customer address #@cust_addr"
    end
    def total_no_of_people
       @@no_of_people += 1
       puts "Total number of people: #@@no_of_people"
    end
end

# Create Objects
cust1=People.new("1", "John", "Apartments, Luda")
cust2=People.new("2", "Poul", "Empire enclave, Kala")

# Call Methods
cust1.total_no_of_people
cust2.total_no_of_people

  

  
 Total number of people: 1
  => nil 
 Total number of people: 2

 

Ruby local variables

Ruby local variables are started with using _ keyword, local variables are used within a scope of class, methods and modules.

  def local_variable
   a = 15
  end
  

Ruby Constants

In ruby Constants start with capital letter, ruby constants can be used with in a class where it has defined.

class Example
   V1 = 100
   V2 = 200
   def show
       puts "Value of first Constant is #{V1}"
       puts "Value of second Constant is #{V2}"
   end
end

# Create Objects
object=Example.new
object.show
  

  Value of first Constant is 100
  Value of second Constant is 200