Comprehensive Ruby Programming

A mailer class

Here we have created a new class called Mailer that has a single method that will send out an email. The email method takes an argument where we can pass the invoice details to it:

class Invoice  def initialize(customer:, state:, total:)    @customer = customer    @state = state    @total = total  end  def details    "Customer: #{@customer}, Total: #{@total}"  end  def sales_tax    case @state    when 'AZ' then 5.5    when 'TX' then 3.2    when 'CA' then 8.7    end  endendclass Mailer  def self.email(content)    puts "Emailing..."    puts content  endendinvoice = Invoice.new(customer: "Google", state: "AZ", total: 100)puts invoice.sales_taxMailer.email(invoice.details) 

If we run this code, we'll see this is working properly:

5.5Emailing invoice...Customer: Google, ...