zhiyinjixu总结：有关继承的几个简单例子

一、有子对象的派生类的构造函数:

#include <iostream>
using namespace std;

class A
{
public:
 A(int tam,int tai):am(tam),ai(tai) {}
public:
       int am;
protected:
          int ai;
};

class B:public A
{public:
        B(int tam,int tai,  int tob_Am,int tob_Ai,  int tbm,int tbx) : A(tam,tai),  ob_A(tob_Am,tob_Ai)  { bm=tbm; bx=tbx; }       //有子对象的派生类的构造函数
public:
       int bm;
       A ob_A;
       void dispaly()
       {
        cout<<ob_A.am<<endl;
       }
private:
        int bx;
};

int main()
{
B ob1(45,5, 9,3, 5,8) ;
cout<<ob1.am<<endl;
cout<<endl;
ob1.dispaly();
}

 

二、多层派生是的构造函数的写法：

#include <iostream>
using namespace std;

class A
{
public:
A(){}
A(int tam,int tai,int tax) : am(tam),ai(tai),ax(tax) {}
public:
        int am;
protected:
  int ai;
private:
        int ax;
public:
  void a_dispaly()
       {
        cout<< am <<endl;
        cout<< ai <<endl;
       cout<< ax <<endl;
       }
};


class B : public A
{
public:
        B (){}
        B (int tam,int tai,int tax,  int tbm,int tbi,int tbx) : A(tam,tai,tbx), bm(tbm),bi(tbi),bx(tbx) {}
public:
       int bm; 
protected:
  int bi;
private:
        int bx; 
public:
 void b_dispaly()
       {        
       a_dispaly();
       cout<< bm <<endl;
        cout<< bi <<endl;
       cout<< bx <<endl;
       }
};

class C : public B
{
public:
        C (){}
        C (int tam,int tai,int tax, int tbm,int tbi,int tbx,  int tcm,int tci,int tcx) : B(tam,tai,tbx,tbm,tbi,tbx), cm(tcm),ci(tci),cx(tcx) {}
public:
       int cm;    
protected:
 int ci;
private:
        int cx; 
public:
 void c_dispaly()
       {        
       b_dispaly();
       cout<< cm <<endl;
        cout<< ci <<endl;
       cout<< cx <<endl;
       }
};

int main()
{
C ob3(5,3,84, 8,1,84,9,5,9);
ob3.c_dispaly();
}

三、有子对象的多层派生类的构造函数：

#include <iostream>
using namespace std;

class A
{
public:
A(){}
A(int tam,int tai,int tax) : am(tam),ai(tai),ax(tax) {}
public:
        int am;
protected:
  int ai;
private:
        int ax;
public:
  void a_dispaly()
       {
        cout<< am <<endl;
        cout<< ai <<endl;
       cout<< ax <<endl;
       }
};

class B : public A
{
public:
        B (){}
        B (int tam,int tai,int tax,  int tbm,int tbi,int tbx) : A(tam,tai,tbx), bm(tbm),bi(tbi),bx(tbx) {}
        B (int tam,int tai,int tax,  int tob_Am,int tob_Ai,int tob_Ax,  int tbm,int tbi,int tbx) : A(tam,tai,tax),  ob_A(tob_Am,tob_Ai,tob_Ax)  { bm=tbm; bi=tbi;bx=tbx; }       //有子对象的派生类的构造函数
public:
       int bm;
       A ob_A;      
protected:
  int bi;
private:
        int bx; 
public:
  void b_dispaly()
       {
        cout<<"子对象的public成员变量am的值是  "<<ob_A.am<<endl;
      a_dispaly();
       cout<< bm <<endl;
        cout<< bi <<endl;
       cout<< bx <<endl;
       }
};

class C: public B
{
public:
 C () {}
 C (int tam,int tai,int tax,  int tbm,int tbi,int tbx,  int tcm,int tci,int tcx) : B(tam,tai,tbx,tbm,tbi,tbx), cm(tcm),ci(tci),cx(tcx) {}
 C (int tam,int tai,int tax,  int tob_Am,int tob_Ai,int tob_Ax,  int tbm,int tbi,int tbx,  int tcm,int tci,int tcx) : B(tam,tai,tbx,tob_Am,tob_Ai,tob_Ax,tbm,tbi,tbx), cm(tcm),ci(tci),cx(tcx) {}
public:
 int cm;
 
protected:
 int ci;
private:
 int cx;
public:
 void c_dispaly()
 {
 b_dispaly(); 
 cout<< cm <<endl;
 cout<< ci <<endl;
 cout<< cx <<endl; 
 } 
};

int main()
{

C ob3(5,3,84, 8,1,89, 99,5,85,2,6,11);
ob3.c_dispaly();
}

四、多重继承的构造函数的书写 ：

#include <iostream>
using namespace std;

class A
{
public:
 A (){}
 A (int tam): am(tam) {}
public:
 int am; 
};

class B
{
public:
 B (){} 
 B (int tbm): bm(tbm) {}
public:
int bm; 
};

class C
{
public:
 C (){} 
 C (int tcm): cm(tcm) {}
public:
 int cm; 
};

class D :  public A,public B,public C
{
public:
 D (){} 
 D (int tm, int tdm) : A(tm),B(tm),C(tm)    { dm=tdm;}   //多重继承的构造函数的书写
public:
int dm; 
};

int main ()
{
 D ob1(5,3);
 cout<<ob1.am<<endl;
 cout<<ob1.bm<<endl;
 cout<<ob1.cm<<endl;
 cout<<ob1.dm<<endl;
}

五、基类和派生类有同名成员：

#include <iostream>
using namespace std;

class A
{
public:
 A (){}
 A (int tam): am(tam) {}
public:
 int am; 
 double n;
};

class B
{
public:
 B (){} 
 B (int tbm): bm(tbm) {}
public:
int bm; 
double n;
};

class D :  public A,public B
{
public:
 D (){} 
 D (int tm, int tdm) : A(tm),B(tm)    { dm=tdm;}   //多重继承的构造函数的书写
public:
int dm; 
double n;
};

int main ()
{
 D ob1(5,3);
 cout<<ob1.am<<endl;
 cout<<ob1.bm<<endl;
 cout<<ob1.dm<<endl;
 
 ob1.n = 33.2;             //基类和派生类有同名成员的时候，默认是派生类的成员；如果要访问基类的成员 ，则应该加上基类名 ；也就是说 ob1.n 和 ob1.D::n 是等价的。
 cout<<ob1.n<<endl;
 ob1.A::n = 55.2;
 cout<<ob1.A::n<<endl; 
}

六、无法判断是走那一条路线：

#include <iostream>
using namespace std;

class N
{
public:
 double n;
};

class A : public N
{
};

class B : public N
{
};

class C :  public A, public B
{
};

int main ()
{
 C ob1;
 ob1.B::n =5.9;    //要访问的是 B 的基类成员
 ob1.A::n =6.5;    //要访问的是 A 的基类成员  
}

七、虚基类：

#include <iostream>
using namespace std;

class N
{
public:
 N () {}
 N (int tnm): nm(tnm) {}
public:
 int nm; 
};

class A : virtual public N
{
public:
 A () {}
 A (int tnm): N(tnm) {}
};

class B : virtual public N
{
public:
 B () {}
 B (int tnm): N(tnm) {}
};

class C :  public A, public B
{
public:
 C () {}
 C (int tnm) : N(tnm), A(tnm), B(tnm) {}
 C (int tnm,int tnm1,int tnm2) : N(tnm), A(tnm1), B(tnm2) {}   //在最后的派生类中不仅要负责对其直接基类进行初始化，还要负责对虚基类初始化
};

int main ()
{
C ob1(5,6,1);
cout<<ob1.nm<<endl; 
}

八、指向基类对象的指针变量也可以指向派生类对象：

#include <iostream>
using namespace std;

class A
{
 public:
 A(int tm)
 {
 m=tm; 
 }
public:
int m;
void display1()  
{
 cout<<m<<endl;
}
};

class B :public A
{
 public:
 B(int tm,int tn) :A(tm)
 {
 n=tn; 
 }
public:
int n;
void display2()  
{
 A::display1();
 cout<<n<<endl;
}  
};

int main()
{
A ob1(4);
B ob2(3,6);
A *pa;
pa = &ob1;
pa->display1();
pa = &ob2;
pa->display1();               //输出结果是3，而不是3  6.因为ob1的类型是A，类A中没有n这个成员，只能赋值给m 

B *pb;
//pb = &ob1;
//pb->display1();           //很显然，这样是不允许的、错误的
pb = &ob2;
pb->display2();
}