Derived Classes派生类

Base class access specifier public public public protected protected protected private private private
C++
In the derived class
public protected no access protected protected no access
#include <iostream> #include <cstring> using namespace std; class Animal { protected:
char name[20]; public:
Animal(char* n); };
C++
15
The Mammal Class
class Mammal : public Animal { protected:
C++
13
Virtual Base Classes
In case of multiple inheritance a derived class can inherit multiple issues of a data member.
Animal
Domestic Mammal
Dog
C++
14
The Animal Class
private private no access
5
The Constructor of a Derived Class
Derived classes don’t inherit constructors and destructors.
The constructor of the derived class: ClassName(list-of-parameters) : C_1(list1), ..., C_n(list_n) { // … }
}; The list of base classes is formed from:
public base_class protected base_class private base_class
C++
3
Example (base class list)
class ClassName : public C_1, …, public C_n {
In this case all inherited f1 functions will be considered virtual.
C++
12
The main Function
int main() { Derived d; d.f2();
}
Output: Base: f2 Derived: f1
public:
virtual void f1();
void f2();
};
If function f1 is declared as virtual, then the selection of the file will be done in running-time.
We have to place only one virtual keyword in front of the declaration of the f1 function, in the base class.
int main() { Output:
Derived d; Base: f2
d.f2();
Base: f1
}
The selection of the f1 function has been done in compile time.
C++
11
Virtual functions
class Base {
C++
6
Example
#include <iostream> using namespace std;
class Base { public:
void f1(); void f2(); };
C++
7
The Derived Class
class Derived : public Base { public:
C++
17
The Dog Class
void f1(); }; Override only the f1 function. Function f2 will be inherited from Base.
C++
8
The Member Functions of the Base Class
void Base::f1()
{
cout << "Base: f1\n";
}
void Base::f2()
{
cout << "Base: f2\n";
f1();
}
C++
9
Member Function of the Derived Class
void Derived::f1() {
cout << "Derived: f1\n"; }
C++
10
The main function
Derived Classes
Outline
Definition Virtual functions Virtual base classes Abstract classes. Pure virtual functions.
C++
2
Definition
class Derived : list-of-base-classes { // new data member and member functions
int weight; public:
Mammal(char* n, int w); };
C++
16
The Domestic Class
class Domestic : public Animal { protected:
int comportment; public:
Domestic(char* n, int c); };
// … }; Class ClassName is derived from:
C_1, ..., C_n.
C++来自4Access Control
In the base class
public protected
private public protected private public protected private