Chương 4: Understanding Object-Oriented Programming Inheritence pps

Chapter 4. Understanding

Object-Oriented

Programming: Inheritance

Hoang Anh Viet

[email protected]

Hanoi University of Technology

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Microsoft

Objectives

“This chapter introduced inheritancethe ability to create classes by

absorbing an existing class's members and enhancing them with new

capabilities. You learned the notions of base classes and derived

classes and created a derived class that inherits members from a base

class. The chapter introduced access modifier protected; derived class

methods can access protected base class members. You learned how to

access base class members with base. You also saw how constructors are

used in inheritance hierarchies. Finally, you learned about Software

Engineering with Inheritance.”

 Introduction

 Base Classes and Derived Classes

 protected and internal Members

 Relationship between Base Classes and Derived Classes

 Constructors and Destructors in Derived Classes

 Extension methods and Inheritance

 Software Engineering with Inheritance

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Roadmap

 4.1 Introduction

 4.2 Base Classes and Derived Classes

 4.3 protected and internal Members

 4.4 Relationship between Base Classes and Derived Classes

 4.5 Constructors and Destructors in Derived Classes

 4.6 Extension methods and Inheritance

 4.7 Software Engineering with Inheritance

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4.1 Introduction

 Defining the Pillars of OOP:

 Encapsulation: How does this language hide an object’s

internal implementation details and preserve data integrity?

 Inheritance: How does this language promote code reuse?

 Polymorphism: How does this language let you treat related

objects in a similar way?

 The Role of Inheritance:

 In essence, inheritance allows you to extend the behavior of a

base (or parent) class by inheriting core functionality into the

derived subclass (also called a child class)

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4.1 Introduction

 Inheritance:

 Classes are created by absorbing the methods and variables of

an existing class

 It then adds its own methods to enhance its capabilities

 This class is called a derived class because it inherits methods

and variables from a base class

 Objects of derived class are objects of base class, but not vice

versa

 “Is a” relationship: derived class object can be treated as base

class object (inheritance)

 “Has a” relationship: class object has object references as

members (composition)

 A derived class can only access non-private base class

members unless it inherits accessor funcitons

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4.1 Introduction

 Types Of Inheritance: what C# does and does not support ?

 Implementation vs. Interface Inheritance

 Implementation inheritance means that a type

derives from a base type, taking all the basetype's

member fields and functions.

 Interface inheritance means that a type inherits only

the signatures of the functions, but does not inherit

any implementations.

 Multiple Inheritance: C# does not support multiple implementation

inheritance. It does, however, allow types to derive from multiple

interfaces.

 Structs and Classes: structs do not support inheritance.

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Roadmap

 4.1 Introduction

 4.2 Base Classes and Derived Classes

 4.3 protected and internal Members

 4.4 Relationship between Base Classes and Derived Classes

 4.5 Constructors and Destructors in Derived Classes

 4.6 Extension methods and Inheritance

 4.7 Software Engineering with Inheritance

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4.2 Base Classes and Derived Classes

 An object often is an object of another class

 Every derived-class is an object of its base class

 Inheritance forms a tree-like heirarchy

 To specify class one is derived from class two

 class one : two

 Composition:

 Formed by “has a” relationships

 Constructors are not inherited

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