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C++知识点案例 笔记-4
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内容图文
1.纯虚函数
2.抽象类
3.内部类
4.运算符重载
5.类的函数重载
6.友元的函数重载
1.纯虚函数
==纯虚函数==
//有时基类中无法给出函数的具体体现，定义纯虚函数可以为派生函数保留一个函数接口
#include <iostream>
#include <cstring>
using namespace std;
class Animal
{
public:
Animal(char *name);
void print_name();
virtual void print_color() = 0;
virtual ~Animal();
private:
char *m_Name;
};
Animal::Animal(char *name)
{
m_Name = new char[strlen(name)+1];
strcpy(m_Name,name);
}
Animal::~Animal()
{
cout<<"Animal diluting !!!"<<endl;
if(m_Name)
{
delete[]m_Name;
}
}
void Animal::print_name()
{
cout<<"name: "<<m_Name<<endl;
}
class Cat:public Animal
{
public:
Cat(char *name,char *color);
virtual void print_color();
virtual ~Cat();
private:
char *m_Color;
};
Cat::Cat(char *name,char *color):Animal(name)
{
m_Color = new char[strlen(color)+1];
strcpy(m_Color,color);
}
void Cat:: print_color()
{
cout<<"Cat color :"<<m_Color<<endl;
}
Cat::~Cat()
{
cout<<"Cat diluting !!!"<<endl;
if(m_Color)
{
delete[]m_Color;
}
}
int main()
{
Animal *p;
p = new Cat("catmimi","yellow");
p->print_name();
p->print_color();
delete p;
return 0;
}
2.抽象类
==抽象类==
//含有纯虚函数的基类，若派生类继承后仍有纯虚函数也为抽象类，直至无纯虚函数为止
#include<iostream>
#include<cstring>
using namespace std;
const double IP = 3.1415926;
class Shapes
{
public:
Shapes(int x,int y = 0);
virtual ~Shapes();
virtual void disp() = 0;
protected:
int m_X,m_Y;
};
Shapes::Shapes(int x,int y)
{
m_X = x;
m_Y = y;
}
Shapes::~Shapes()
{
cout<<"Shapes diluting !!!"<<endl;
}
class Squre:public Shapes
{
public:
Squre(int squre_x,int squre_y);
virtual void disp();
virtual ~Squre();
};
Squre::Squre(int squre_x,int squre_y):Shapes(squre_x,squre_y)
{
}
void Squre::disp()
{
cout<<"The squre area:"<<m_X*m_Y<<endl;
}
Squre::~Squre()
{
cout<<"Squre diluting !!!"<<endl;
}
class Circle:public Shapes
{
public:
Circle(int R);
virtual void disp();
virtual ~Circle();
};
Circle::Circle(int R):Shapes(R)
{
}
void Circle::disp()
{
cout<<"The circle area : "<<IP * m_X * m_X<<endl;
}
Circle::~Circle()
{
cout<<"Circle diluting !!!"<<endl;
}
int main()
{
Shapes *p[2];
p[0] = new Squre(5,10);
p[0] ->disp();
p[1] = new Circle(2);
p[1] ->disp();
for(int i;i<2;i++)
{
delete p[i];
}
return 0;
}
3.内部类
==内部类==
//在（基）类内部定义的类叫做内部类，（基）类相当于该类的外部类
#include <iostream>
using namespace std;
class Outer
{
public:
class Inner{
private:
int Inner_n;
public:
void set_outer_n(Outer &ref_outer){ref_outer.outer_n = 100;}
void set_inner_n(){Inner_n = 666;}
void show(Outer &ref_outer)
{
ref_outer.show();
cout<<"Inner: "<<Inner_n<<endl;
}
};
void show(){cout<<"Out: "<<outer_n<<endl;}
private:
int outer_n;
};
int main()
{
Outer outer_ojb;
Outer::Inner inner_ojb;
inner_ojb.set_outer_n(outer_ojb);
inner_ojb.set_inner_n();
inner_ojb.show(outer_ojb);
return 0;
}
4.运算符重载
==运算符重载==
//如对象的相加，把特殊符号定义为函数易于表达
#include<iostream>
using namespace std;
class Q
{
private:
int x,y;
public:
Q(int x1=0,int y1=0):x(x1),y(y1){}
void show() const;
Q operator + (const Q&a)const ;###########重载+运算符
Q operator - (const Q&a)const ;
};
void Q::show() const
{
cout<<"(x,y)="<<"("<<x<<","<<y<<")"<<endl;
}
Q Q::operator + (const Q&a)const
{
return Q(x + a.x,y + a.y);
}
Q Q::operator - (const Q&a)const
{
return Q(x - a.x,y - a.y);
}
int main()
{
Q a1(7,2);
Q a2(5,1);
Q a;
Q b;
a = a1 + a2;
b = a1 - a2;
cout<<"a1:";
a1.show();
cout<<"a2:";
a2.show();
cout<<"a:";
a.show();
cout<<"b:";
b.show();
cout<<"a1+a2:";
a.show();
cout<<"a1-a2:";
b.show();
return 0;
}
5.类的函数重载
==类的函数重载==
#include<iostream>
using namespace std;
class V
{
private:
int a,b;
public:
V(int a1 = 0,int b1 = 0):a(a1),b(b1){}
void show() const;
V operator ++();
V operator ++(int);
};
void V::show() const
{
cout<<"(a,b)="<<"("<<a<<","<<b<<")"<<endl;
}
V V::operator ++() //++前置函数
{
++a;
++b;
return *this;
}
V V::operator ++(int) //"k=i++"：后缀++表示先k=i之后i自增
{
V a = *this;
++(*this); //调用前置函数
return a;
}
int main()
{
V m(1,1);
V n(0,0);
(m++).show();
(++n).show();
return 0;
}
6.友元的函数重载
==友元的函数重载==
//定义时不用指明函数位置，方便私有数据成员的调用
#include<iostream>
using namespace std;
class G
{
private:
int m,n;
public:
G(int m1 = 0,int n1 = 0):m(m1),n(n1){}
void show() const;
friend G operator + (const G&a1,const G&a2);
friend G operator - (const G&a1,const G&a2);
};
void G::show() const
{
cout<<"(m,n)="<<"("<<m<<","<<n<<")"<<endl;
}
G operator + (const G&a1,const G&a2)
{
return G(a1.m +a2.m , a1.n +a2.n);
}
G operator - (const G&a1,const G&a2)
{
return G(a1.m - a2.m, a1.n - a2.n);
}
int main()
{
G j(2,2);
G k(1,1);
G a;
j.show();
k.show();
a.show();
a = j + k;
a.show();
a = j - k;
a.show();
return 0;
}
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