12.5 Summary

Swift structures and classes both provide a mechanism for creating instances that define properties, store values and define methods. Although the two mechanisms appear to be similar, there are significant behavioral differences when structure and class instances are either copied or passed to a method. Classes are categorized as being reference type instances while structures are value type. When a structure instance is copied or passed, an entirely new copy of the instance is created containing its own data. Class instances, on the other hand, are passed and copied by reference, with each reference pointing to the same class instance. Other features unique to classes include support for inheritance and deinitialization and the ability to identify the class type at runtime. Structures should typically be used in place of classes unless specific class features are required.

Enumerations are used to create custom types consisting of a pre-defined set of state values...