Wk 4a - Class Hierarchy

Synopsis:

This lecture provides an introduction to structuring designs with C++ classes and their relationships. We will cover basic ideas in a presentation and then discuss code examples.

Readings and Activities for the Week:

CPPPL: Chapters 16 - 21, focusing on Chapter 21.
Review requirements for your second Project assignment: Projects > Project #2
Look carefully at Compound Objects code.

Glossary of Terms

Class:
A language construct that binds together member functions and data:
- Class syntax: class X { ... }
- Method syntax: R X::f(T t) { ... }
- Data syntax: Y y;
We normally reserve the term "method" for member functions of a class, and use the term "function" for functions that are not bound to any class. Another common term describes these unbound functions as "global functions".
Class Relationships:
Object Oriented Designs use C++ classes and their relationships to structure an implementation. The relationships are:
- Inheritance:
  Derived classes specialize base classes, using the syntax:
```
  class D : public B { ... };
```
- Composition:
  Composing classes hold instances of other types as data members, using the syntax:
```
  class C 
  { 
    ... 
  private:
    A a;
    B b;
  };
```
- Aggregation:
  Aggregating classes hold pointers to instances of data on the native heap, using the syntax:
```
  class A 
  { 
    ... 
  private:
    B* pB = nullptr;
    C* pC = nullptr;
  };
```
  The pointers are initialized to point to heap allocations in some member function of the class, perhaps in it's constructors and the allocations are returned in its destructor.
- Using:
  Using classes are passed class instances they will use through member function calls. They do not own these instances, simply use them temporarily, with the syntax:
```
  class U 
  { 
    void usingMF(R* pR)
    {
      pr->someUsefulFunction();
    }
  };
```

Lecture Content:

Projects:
- Sample Project #1, Code folder
  Lexical scanner
- Sample Project #2. Code folder
  Rule-based parser
- Sample Project #3, Code folder
  Parser with Abstract Syntax Tree
- Sample Project #4, Code folder
  Code Analyzer
Class Hierarchy
- class relationships, docx, class relationships - layout view, vsdx, ClassRelationships code folder
  Illustrates static (class) and physical (memory) structure.
- Hierarchy Presentation, pptx
  Hierarchy is concerned with the relationships between classes - aggregation, composition, inheritance, and using.
- Principles - esp. Liskov Substitution
  Discussion of principles that guide good Object Oriented Design
- Virtual Function Pointer Tables, vsdx
  Virtual Function Pointer Tables
- Demonstrates Compound Object creation
  You need to understand how constructor initialization is used to control creation of the objects you use.
- Three Tier Hierarchy
  Interface defines a contract, abstract base class provides sharing, derived classes implement the contract in specialized ways.
- Demonstrate Composition
  This project contains several demonstrations of basic composition relationships.
- Demonstrate Inheritance
  Contains demonstration of things to be careful with when using inheritance.
- C++'s Dark Corners, docx
  A summary of the short list, with brief explainations, of C++'s dark corners, e.g., things that can cause subtle errors.
Preparation for Synchronous Discussion:
- Create a class diagram for your Project #2 implementation. Please indicate all of the class relationships.
- Be prepared to discuss your packages and dependencies.
Lecture Take-aways:
The most important things we discussed today:
- class relationships, docx, class relationships - layout view, vsdx
- Class Hierarchies, pptx

Week 4a - Class Hierarchy

Classes and Class Relationships

Synopsis:

Readings and Activities for the Week:

Glossary of Terms

Class:

Class Relationships:

Lecture Content:

Projects:

Class Hierarchy

Preparation for Synchronous Discussion:

Lecture Take-aways: