1 / 66

CHAPTER 10 Inheritance 继承

CHAPTER 10 Inheritance 继承. Introduction

erica
Download Presentation

CHAPTER 10 Inheritance 继承

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CHAPTER 10Inheritance继承 Introduction A key feature of an object-oriented language in inheritance. Inheritance is the ability to define new classes using existing classes as a basis. The new class inherits the attributes and behaviors of the classes on which it is based, and it can also have attributes and behaviors that are specific to it. 继承是面向对象语言的重要特征之一。继承是把已有类作为基类定义新的类。这个新的类继承了基类的属性和操作，而且还可以具有自己特定的属性和操作。

  2. 10.1 OBJECT-ORIENTED DESIGN USING INHERITANCE • Three relationships are commonly used in object-oriented design : • is-a relationships • Hierarchy relationship. It specifies that one abstraction is a specialization • of another. • has-a relationships • Contain relationship. Some object is part of another. • uses-a relationships • One object uses another object in some way.

  3. B1 B2 C2 C1 is-a relationships A Base class of B1 and B2 Derived class of A Base class of C1, C2 and C3 Derived class of A Base class of C3 Derived class of B1 C3 Derived class of B1 and B2 Multiple inheritance

  4. has-a relationships class A { … B DMi … FM } ; class B { … DM … FM } ;

  5. uses-a relationships class A { … DM … FMj ( B & … ) } ; class B { … DM … FM } ;

  6. 10.3.1 Declaring a derived class class DerivedClass : public BaseClass { public : // public section … private : // private section … } ;

  7. 10.3.1 Declaring a derived class classDerivedClass: public BaseClass { public : // public section … private : // private section … } ; Derived class name

  8. 10.3.1 Declaring a derived class class DerivedClass : public BaseClass { public : // public section … private : // private section … } ; Access specifier (usually public)

  9. 10.3.1 Declaring a derived class class DerivedClass : public BaseClass{ public : // public section … private : // private section … } ; Class name of base class

  10. Example Declare vehicle class and derived class car： class vehicle{ public : void initialize (int in_wheels , float in_weight ) ; int get_wheels ( ) ; float get_weight ( ) ; float get_loading ( ) ; private : int wheels ; float weight ; float loading ; }； class car: publicvehicle{ public : void initialize ( int in_wheels , float in_weight , int people = 4 ) ; int passengers ( ) ; private : int passenger_load ; }；

  11. 10.3.2 Implementing a derived class The syntax for the constructor of derived class is DClass :: DClass ( Plist ) : BClass ( Plist ) , DMbrList { // Body of derived class constructor … }

  12. 10.3.2 Implementing a derived class The syntax for the constructor of derived class is DClass :: DClass ( Plist ) : BClass ( Plist ) , DMbrList { // Body of derived class constructor … } Derived class name

  13. 10.3.2 Implementing a derived class The syntax for the constructor of derived class is DClass :: DClass ( Plist ) : BClass ( Plist ) , DMbrList { // Body of derived class constructor … } Derived class constructor parameter list

  14. 10.3.2 Implementing a derived class The syntax for the constructor of derived class is DClass :: DClass ( Plist ) : BClass ( Plist ) , DMbrList { // Body of derived class constructor … } Base class name

  15. 10.3.2 Implementing a derived class The syntax for the constructor of derived class is DClass :: DClass ( Plist ) : BClass ( Plist ) , DMbrList { // Body of derived class constructor … } Base class constructor parameter list

  16. 10.3.2 Implementing a derived class The syntax for the constructor of derived class is DClass :: DClass ( Plist ) : BClass ( Plist ) , DMbrList { // Body of derived class constructor … } Class data member initialization list

  17. 10.3.2 Implementing a derived class The syntax for the constructor of derived class is DClass :: DClass ( Plist ) : BClass ( Plist ) , DMbrList { // Body of derived class constructor … } • First base class • Second class data member • Last derived class

  18. // Example13-1 #include < iostream.h > class Base { public : Base ( ) { cout << "\nBase created.\n" ; } } ; class D_class : public Base { public : D_class ( ) { cout << "D_class created.\n" ; } } ; void main () { D_class d1 ; } Base created. D_class created. Output

  19. // Example13-2 #include <iostream.h> class parent_class { int private1 , private2 ; public : parent_class ( int p1 , int p2 ) { private1 = p1; private2 = p2; } int inc1 ( ) { return ++private1; } int inc2 ( ) { return ++private2 ; } void display ( ) { cout << "private1=" << private1 << " , private2=" << private2 << endl ; } }; Base class constructor parameter list

  20. class derived_class : private parent_class { int private3 ; parent_class private4 ;// Class data member public: derived_class ( int p1 , int p2 , int p3 , int p4 , int p5 ) : parent_class ( p1 , p2 ) , private4 ( p3 , p4 ) { private3 = p5 ; } int inc1 ( ) { return parent_class :: inc1 ( ) ; } int inc3 ( ) { return ++private3 ; } void display ( ) { parent_class :: display ( ) ; private4 . display ( ); cout << "private3=" << private3 << endl ; } } ; void main ( ) { derived_class d1 ( 17 , 18 , 1 , 2 , -5 ) ; d1 . inc1 ( ) ; d1 . display ( ) ; } Five parameters of derived class constructor

  21. class derived_class : private parent_class { int private3 ; parent_class private4 ;// Class data member public: derived_class( int p1 , int p2 , int p3 , int p4 , int p5 ) : parent_class ( p1 , p2 ) , private4 ( p3 , p4 ) { private3 = p5 ; } int inc1 ( ) { return parent_class :: inc1 ( ) ; } int inc3 ( ) { return ++private3 ; } void display ( ) { parent_class :: display ( ) ; private4 . display ( ) ; cout << "private3=" << private3 << endl ; } } ; void main ( ) { derived_class d1 ( 17 , 18 , 1 , 2 , -5 ) ; d1 . inc1 ( ) ; d1 . display ( ) ; } For base class parent_class(p1,p2) Initialize private1 and private2

  22. class derived_class : private parent_class { int private3 ; parent_class private4 ;// Class data member public: derived_class( int p1 , int p2 , int p3 , int p4 , int p5 ) : parent_class ( p1 , p2 ) , private4 ( p3 , p4 ) { private3 = p5 ; } int inc1 ( ) { return parent_class :: inc1 ( ) ; } int inc3 ( ) { return ++private3 ; } void display ( ) { parent_class :: display ( ) ; private4 . display ( ) ; cout << "private3=" << private3 << endl ; } } ; void main ( ) { derived_class d1 ( 17 , 18 , 1 , 2 , -5 ) ; d1 . inc1 ( ) ; d1 . display ( ) ; } For class member private4 parent_class(p1,p2) : initialize private4.private1 and private4.private2

  23. class derived_class : private parent_class { int private3 ; parent_class private4 ;// Class data member public: derived_class( int p1 , int p2 , int p3 , int p4 ,int p5 ) : parent_class ( p1 , p2 ) , private4 ( p3 , p4 ) { private3 = p5 ; } int inc1 ( ) { return parent_class :: inc1 ( ) ; } int inc3 ( ) { return ++private3 ; } void display ( ) { parent_class :: display ( ) ; private4 . parent_class :: display ( ) ; cout << "private3=" << private3 << endl ; } } ; void main ( ) { derived_class d1 ( 17 , 18 , 1 , 2 , -5 ) ; d1 . inc1 ( ) ; d1 . display ( ) ; } For derived class Initialize data member private3

  24. class derived_class : private parent_class { int private3 ; parent_class private4 ; // Class data member public: derived_class( int p1 , int p2 , int p3 , int p4 ,int p5 ) : parent_class ( p1 , p2 ) , private4 ( p3 , p4 ) { private3 = p5 ; } int inc1 ( ) { return parent_class :: inc1 ( ) ; } int inc3 ( ) { return ++private3 ; } void display ( ) { parent_class :: display ( ) ; private4 . parent_class :: display ( ) ; cout << "private3=" << private3 << endl ; } } ; void main ( ) { derived_class d1 ( 17 , 18 , 1 , 2 , -5 ) ; d1 . inc1 ( ) ; d1 . display ( ) ; } Output private1 = 18 , private2 = 18 private1 = 1 , private2 = 2 private3 = -5

  25. 10.4 PROTECTED MEMBERS AND INHERITANCE保护成员与继承 • Data members and member functions can be cover in the derived class. • The derived class member functions do not access to the private member • of base class.

  26. Example class base { public : int a ,b ; }; class derived : public base { public : int b , c ; } ; void f ( ) { derived d ; d . a = 1 ; d . base :: b = 2 ; // use member b of base class d .b = 3 ; // use member b of derivedclass d . c = 4 ; };

  27. Example class X { public : void get_ij ( ) ; void put_ij ( ) ; private : int i , j ; }; class Y : public X { public : int get_k ( ) ; void make_k ( ) ; private : int k ; }; void Y :: make_k ( ) ; { k = i * j ; // illegal } ;

  28. Example class X { public : void get_ij ( ) ; void put_ij ( ) ; private : int i , j ; }; class Y : public X { public : int get_k ( ) ; void make_k ( ) ; private : int k ; }; void Y :: make_k ( ) ; { k = i * j ; // illegal } ; protected : int i , j ; k = i * j ; // legal

  29. 10.5 CONTROLLING INHERITANCE 控制继承 10.5.1 Public Inheritance 公有继承 class DerivedClass : public BaseClass { public : // public section … private : // private section … } ; The public members and protected members keep their character in derived class.

  30. class X class Y class Z // Example13-3 #include<iostream.h> class X { public : void get_ij( ) { cout << "Enter two numbers:" ; cin >> i >> j ; }; void put_ij( ) { cout << i << " " << j << '\n' ; }; protected : int i , j ; }; class Y : public X { public : int get_k( ) { return k ; }; void make_k( ) { k = i * j; }; // use base class DM private : int k ; }; class Z : public Y { public : void f( ) { i= 2 ; j= 3; }; // use base class DM }; void main ( ) { Y var1; Z var2 ; var1.get_ij( ) ; var1.put_ij( ) ; var1.make_k( ) ; var2.f( ) ; var2.put_ij( ) ; }

  31. 10.5.2 Private inheritance 私有继承 class DerivedClass : private BaseClass { public : // public section … private : // private section … } ; The public members and protected members of base class are private member in derived class.

  32. // Example13-4 #include<iostream.h> class X { public : void get_ij( ) { cout << "Enter two numbers:" ; cin >> i >> j ; }; void put_ij( ) { cout << i << " " << j << '\n' ; }; protected : int i , j ; }; class Y : public X { public : int get_k( ) { return k ; }; void make_k( ) { k = i * j; }; // use base class DM private : int k ; }; class Z : public Y { public : void f( ) { i= 2 ; j= 3; }; // use base class DM }; void main ( ) { Y var1; Z var2 ; var1.get_ij( ) ; var1.put_ij( ) ; var1.make_k( ) ; var2.f( ) ; var2.put_ij( ) ; }

  33. class X private class Y public class Z // Example13-4 #include<iostream.h> class X { public : void get_ij( ) { cout << "Enter two numbers:" ; cin >> i >> j ; }; void put_ij( ) { cout << i << " " << j << '\n' ; }; protected : int i , j ; }; class Y : private X { public : int get_k( ) { return k ; }; void make_k( ) { k = i * j; }; // use base class DM private : int k ; }; class Z : public Y { public : void f( ) { i= 2 ; j= 3; }; // use base class DM }; void main ( ) { Y var1; Z var2 ; var1.get_ij( ) ; var1.put_ij( ) ; var1.make_k( ) ; var2.f( ) ; var2.put_ij( ) ; } OK i, j are private member in Y class

  34. class X private class Y public class Z // Example13-4 #include<iostream.h> class X { public : void get_ij( ) { cout << "Enter two numbers:" ; cin >> i >> j ; }; void put_ij( ) { cout << i << " " << j << '\n' ; }; protected : int i , j ; }; class Y : private X { public : int get_k( ) { return k ; }; void make_k( ) { k = i * j; }; // use base class DM private : int k ; }; class Z : public Y { public : void f( ) { i= 2 ; j= 3; }; // use base class DM }; void main ( ) { Y var1; Z var2 ; var1.get_ij( ) ; var1.put_ij( ) ; var1.make_k( ) ; var2.f( ) ; var2.put_ij( ) ; } Illegal Can not access private member of base class

  35. class X private class Y public class Z // Example13-4 #include<iostream.h> class X { public : void get_ij( ) { cout << "Enter two numbers:" ; cin >> i >> j ; }; void put_ij( ) { cout << i << " " << j << '\n' ; }; protected : int i , j ; }; class Y : private X { public : int get_k( ) { return k ; }; void make_k( ) { k = i * j; }; // use base class DM private : int k ; }; class Z : public Y { public : void f( ) { i= 2 ; j= 3; }; // use base class DM }; void main ( ) { Y var1; Z var2 ; var1.get_ij( ) ; var1.put_ij( ) ; var1.make_k( ) ; var2.f( ) ; var2.put_ij( ) ; } Illegal main() can not call private MF of any objects

  36. 10.5.3 Protected inheritance 保护继承 class DerivedClass : protected BaseClass { public : // public section … private : // private section … } ; The public members and protected members of base class are protected member in derived class. Protected inheritance is used rarely.

  37. Derived Derived class B : public A class C : private A Common functions Such as : main() Do you know how access x, y and z public : x class A protected : y private : z

  38. class A class B 10.6 MULTIPLE INHERITANCE 多继承 A derived class can inherit from two or more base class. class C : public A ，public B

  39. 10.6 MULTIPLE INHERITANCE 多继承 A derived class can inherit from two or more base class. The syntax for declaring a class derived using multiple inheritance is classDClass: publicBClass, publicBClass{ public : // public section … private : // private section … } ;

  40. class A class B class C // Example13-4 #include<iostream.h> class A { public : void setA ( int x ) { a = x ; } ; void showA( ) { cout << a << endl ; } ; private : int a ; } ; class B { public : void setB ( int x ) { b = x ; } ; void showB ( ) { cout << b << endl ; } ; private : int b ; } ; class C : public A , private B { public : void setC ( int x , int y , int z ) { setA ( x ) ; setB ( y ) ; c = z ; } ; void showC ( ) { showA ( ) ; showB ( ) ; cout << c << endl ; } ; private : int c ; } ; void main ( ) { C obj ; obj . setA ( 5 ) ; obj . showA ( ) ; obj . setC ( 6 , 7 , 9 ) ; obj . showC ( ) ; //obj . setB ( 6 ) ; // error, private inheritance //obj . showB ( ) ;// error }

  41. 10.7 VIRTUAL BASE CLASS • If a derived class be derived from multiple base classes, and these base • have a common base class, then, when access members of this common • base class may be open to different interpretations.

  42. class B { b } class B { b } Example class B { public : int b ;} ; class B1 : public B { private : int b1 ; } ; class B2 : public B { private : int b2 ; } ; class C : public B1 , public B2 { public : int f ( ) ; private : int d ; } ; class B1 { b1 } class B2 {b2} class C { f () , d } … C c ; c . b// error c . B :: b // error，where from? c . B1 :: b // ok，from B1 c . B2 :: b // ok ，from B2

  43. class B { b } class B { b } class B1 { b1 } class B2 {b2} class C { f () , d } // Example13-5 #include<iostream.h> class B{public: int b;}; class B1:public B {public: int b1;}; class B2:public B {public: int b2;}; class C:public B1, public B2 {public: f(); private: int b1;}; void main() { C c; c.B1::b=5; c.B2::b=10; cout<<"path B1==>"<<c.B1::b<<endl; cout<<"path B2==>"<<c.B2::b<<endl; } Output: path B1==> 5 path B2==> 10

  44. class B { b } class B { b } class B1 { b1 } class B2 {b2} class C { f () , d } b b1 B b B1 b2 B C d B2 Example class B { public : int b ;} ; class B1 : public B { private : int b1 ; } ; class B2 : public B { private : int b2 ; } ; class C : public B1 , public B2 { public : int f ( ) ; private : int d ; } ; Store of multiple derived class object C When create object C, constructor of B is called two times. Once for B1, Others for B2. A C object contains two sub-object of B.

  45. 10.7 VIRTUAL BASE CLASS • If a derived class be derived from multiple base classes, and these base • have a common base class, then, when access members of this common • base class may be open to different interpretations. • For produce only one sub-object in deriver class object, the base classes must be declared virtual inheritance the common base class. Key word virtual

  46. class B1 { b1} class B2 {b2} Example class B { public : int b ;} ; class B1 : virtual public B { private : int b1 ; } ; class B2 : virtual public B { private : int b2 ; } ; class C : public B1 , public B2 { private : float d ; } ; class B { b } As: C cc ; cc . b// OK class C { d } cc . B1 :: b and cc . B2 :: b is same sub-object of class B

  47. class B { b } class B1 { b1} class B2 {b2} class C { d } b1 B1 C b2 B2 d b B Example class B { public : int b ;} ; class B1 : virtual public B { private : int b1 ; } ; class B2 : virtual public B { private : int b2 ; } ; class C : public B1 , public B2 { private : float d ; } ; Store of object C using virtual inheritance

  48. 10.7 VIRTUAL BASE CLASS • If a derived class be derived from multiple base classes, and these base • have a common base class, then, when access members of this common • base class may be open to different interpretations. • For produce only one sub-object in deriver class object, the base classes must be declared virtual inheritance the common base class. • Using virtual inheritance, the constructor of common base class is called only once.

  49. // Example13-6 #include < iostream.h > class A { public : A ( ) { cout << "class A" << endl ; } } ; class B : virtual public A { public : B ( ) {cout << "class B" << endl ; } } ; class C : virtual public A { public : C ( ) {cout << "class C" << endl ; } } ; class D : public B , public C { public : D ( ) {cout << "class D" << endl ; } } ; void main ( ) { D dd ; } class A class B class C class D Output

More Related