Let's consider three services--CustomerInformationService, MailService, and EmailService, which can provide the capabilities listed earlier. We can create NewCustomerService with the following steps:
- Call CustomerInformationService to save customer information to the database.
- Call MailService to mail the welcome kit.
- Call EmailService to send the e-mail notification.
NewCustomerService becomes the central place for all business logic. Imagine if we have to do more things when a new customer is created. All that logic would start accumulating and bloating up NewCustomerService.