Chapter 10. Study Guide

Object-oriented programs typically consist of many objects bound together to form a complete program. The binding enables objects to communicate, and through this communication, they cooperate to solve the problem for which we wrote the program. The Unified Modeling Language (UML) recognizes five different relationships that bind objects together. C++ is not limited to binding objects with the UML relationships, nor is the UML necessary for writing object-oriented programs. Nevertheless, the UML provides a convenient way of identifying and communicating object-oriented concepts, making it a helpful tool for learning how to create multi-class programs. Chapter 10 demonstrates how to build programs consisting of multiple objects instantiated from multiple classes, and how to use the binding relationships to solve programming problems.

Please focus on the following as you study Chapter 10:

• Meaning. The classes and objects in a program correspond to entities in the "real world" - formally the problem domain. The classes in an object-oriented program reflect (or exhibit) the problem-relevant characteristics of real-world entities - their data and operations (what they do). Similarly, the relationships between classes also have meaning that reflects how those entities connect and interact in the real world.
• Terminology. Chapter 10 introduces a great deal of new terminology. You must focus on, learn, and remember that terminology.
• Syntax. Understandably, building connections between classes requires us to learn additional C++ syntax. The new syntax and the associated concepts extend the syntax and concepts introduced in previous chapters. So, you must review any previous material that is unclear.

Study Aids

• Test Yourself Questions
• Blank Class Relationship Worksheets
• Self-Testing
  • Chapter 10 Study Guide
  • Chapter 10 Study Guide Answers

Know

• UML class diagrams with a single class
• Class diagrams consisting of individual classes connected by class relationships
• The meaning of each UML class relationship
• The roles each class plays in a class relationship
• The general (non-computer science) meaning of hierarchy
• The meaning of inheritance, composition, and aggregation hierarchies
• Peer-to-peer relationships with one-to-one association (know about many-to-one and many-to-many associations)
• The meaning and use of a forward declaration
• How to implement the class relationships in C++ (similar to recognizing them - see below)
• How to use header files while implementing class relationships
  • #ifndef/#endif
  • #pragma once
  • class class-name;        //a forward declaration: only works with pointers
• How to recognize a class relationship by its UML symbol (at right)
• How to recognize a class relationship by its C++ code pattern

  	Inheritance	Composition	Aggregation	Dependency
  class Foo { ... };	class Bar : public Foo { ... };	class Bar { private: Foo f; };	class Bar { private: Foo* f; };	class Bar { public: void function(Foo f) {...} };

  Association
  class Foo; // forward declaration (pointer only) class Bar { private: Foo* f; };	class Bar; // forward declaration (pointer only) class Foo { private: Bar* b; };

• How to chain constructor calls when implementing class relationships
• How to chain member function calls when implementing class relationships