Ruby Class Example

The following will create a Ruby class named Customer, declaring two methods:

• display_details: This method is used to display the customer's detailed information.
• total_no_of_customers: This method is used to display the total number of customers created in the system.

Example

#!/usr/bin/ruby

class Customer
   @@no_of_customers = 0
   def initialize(id, name, addr)
      @cust_id = id
      @cust_name = name
      @cust_addr = addr
   end
   def display_details()
      puts "Customer id #@cust_id"
      puts "Customer name #@cust_name"
      puts "Customer address #@cust_addr"
   end
   def total_no_of_customers()
      @@no_of_customers += 1
      puts "Total number of customers: #@@no_of_customers"
   end
end

The display_details method contains three puts statements that display the customer ID, customer name, and customer address. The puts statement:

puts "Customer id #@cust_id"

will display the text "Customer id" and the value of the variable @cust_id on a single line.

When you want to display the text and value of an instance variable on a single line, you need to place the symbol (#) in front of the variable name in the puts statement. The text and the instance variable with the symbol (#) should be enclosed in double quotes.

The second method, total_no_of_customers, contains the class variable @@no_of_customers. The expression @@no_of_customers += 1 increments the variable no_of_customers by 1 each time the total_no_of_customers method is called. This way, you will get the total number of customers in the class variable.

Now, create two customers as follows:

cust1 = Customer.new("1", "John", "Wisdom Apartments, Ludhiya")
cust2 = Customer.new("2", "Poul", "New Empire road, Khandala")

Here, we created two objects of the Customer class, cust1 and cust2, and passed the necessary parameters to the new method. When the initialize method is called, the necessary attributes of the object are initialized.

Once the objects are created, you need to use the objects to call the methods of the class. If you want to call a method or any data member, you can write the code as follows:

cust1.display_details()
cust1.total_no_of_customers()

The object name is always followed by a dot, followed by the method name or data member. We have seen how to call the two methods using the cust1 object. Using the cust2 object, you can also call the two methods as follows:

cust2.display_details()
cust2.total_no_of_customers()

Save and Execute the Code

Now, put all the source code in a file named main.rb, as follows:

Example

#!/usr/bin/ruby

class Customer
   @@no_of_customers = 0
   def initialize(id, name, addr)
      @cust_id = id
      @cust_name = name
      @cust_addr = addr
   end
   def display_details()
      puts "Customer id #@cust_id"
      puts "Customer name #@cust_name"
      puts "Customer address #@cust_addr"
   end
   def total_no_of_customers()
      @@no_of_customers += 1
      puts "Total number of customers: #@@no_of_customers"
   end
end

# Create objects
cust1 = Customer.new("1", "John", "Wisdom Apartments, Ludhiya")
cust2 = Customer.new("2", "Poul", "New Empire road, Khandala")

# Call methods
cust1.display_details()
cust1.total_no_of_customers()
cust2.display_details()
cust2.total_no_of_customers()

Then, run the program as follows:

$ ruby main.rb

This will produce the following result:

Customer id 1
Customer name John
Customer address Wisdom Apartments, Ludhiya
Total number of customers: 1
Customer id 2
Customer name Poul
Customer address New Empire road, Khandala
Total number of customers: 2