Communication among classes

Up until now, we've described classes and, by extension, Unity components, as separate standalone entities; in reality, they are deeply intertwined. You'd be hard-pressed to create any kind of meaningful software application without invoking some kind of interaction or communication between classes.

If you remember the post-office example from earlier, the example code made use of periods (or dots) to reference classes, variables, and methods. If you think of classes as directories of information, then dot notation is the indexing tool: 

PostOffice.Address

Any variables, methods, or other data types within a class can be accessed with dot notation. This applies to nested, or subclass information as well, but we'll tackle all those subjects when we get to Chapter 5, Working with Classes and Object-Oriented Programming. 

Dot notation is also what drives communication between classes. Whenever a class needs information about another class or wants to execute one of its methods, dot notation is used:

PostOffice.DeliverMail()

Dot notation is sometimes referred to as (.) Operator, so don't be thrown off if you see it mentioned this way in the documentation.

If dot notation doesn't quite click with you yet, don't worry, it will. It's the bloodstream of the entire programming body, carrying information and context wherever it's needed.