524: Mainline

The rabbits simulation illustrates typical application construction: Smalltalk applications typically are built around an application instance, which is the sole instance of an application class. The application instance typically has two roles:

• The application instance holds onto the application's key values via instance variables.
• The application instance is the receiver of one or more messages that establish initial variable values and launch the application.

The rabbit-simulation application developed in this chapter is centered on an instance of the RabbitApplication class, which contains rabbits, month, and history instance variables. The initialize and tickTo: messages initialize variable values and launch the application. The argument supplied with the tickTo: message specifies how much time is to be simulated.