C++ 继承详解及实例代码

　C++继承可以是单一继承或多重继承，每一个继承连接可以是public,protected,private也可以是virtual或non-virtual。然后是各个成员函数选项可以是virtual或non-virtual或pure virtual。本文仅仅作出一些关键点的验证。

　　public继承，例如下：

1 class base
2 ｛...｝
3 class derived:public base
4 ｛...｝

　　如果这样写，编译器会理解成类型为derived的对象同时也是类型为base的对象，但类型为base的对象不是类型为derived的对象。这点很重要。那么函数形参为base类型适用于derived，形参为derived不适用于base。下面是验证代码，一个参数为base的函数，传入derived应该成功执行，相反，一个参数为derived的函数

#include 
#include 

class base
{
  public:
  base()
  :baseName(""),baseData(0)
  {}
  
  base(std::string bn,int bd)
  :baseName(bn),baseData(bd)
  {}
  
  std::string getbaseName() const
  {
    return baseName;
  }
  
  int getbaseData()const
  {
    return baseData;
  }
  
  private:
    std::string baseName;
    int baseData;
};

class derived:public base
{
  public:
    derived():base(),derivedName("")
    {}
    derived(std::string bn,int bd,std::string dn)
    :base(bn,bd),derivedName(dn)
    {}
    std::string getDerivedName() const
    {
      return derivedName;
    }
  private:
    std::string derivedName;
};

void show(std::string& info,const base& b)
{
  info.append("Name is ");
  info.append(b.getbaseName());
  info.append(", baseData is ");
  char buffer[10];
  sprintf(buffer,"%d",b.getbaseData());
    info.append(buffer);
}

int main(int argc,char* argv[])
{
  base b("test",10);
  std::string s;
  show(s,b);
  std::cout<

运行结果为：
base:baseName is test, baseData is 10

base:baseName is btest, baseData is 5


下面改改代码，将函数参数变为derived

void show2(std::string& info,const derived& d)
{
  info.append("Name is ");
  info.append(d.getbaseName());
  info.append(", baseData is ");
  char buffer[10];
  sprintf(buffer,"%d",d.getbaseData());
  info.append(buffer);
}


调用show(ss,d);编译器报错

1 derived_class.cpp: In function `int main(int, char**)':
2 derived_class.cpp:84: error: invalid initialization of reference of type 'const derived&' from expression of type 'base'
3 derived_class.cpp:70: error: in passing argument 2 of `void show2(std::string&, const derived&)'


第二点对各种形式的继承作出验证，首先给出表格


  

    

      
继承方式成员类型
      
public
      
protected
      
private
    
    

      
public
      
public
      
protected
      
无法继承
    
    

      
protected
      
protected
      
protected
      
无法继承
    
    

      
private
      
private
      
private
      
无法继承
    
  


这里解释一下，这里仅仅表达基类的成员，被public,protected,private三种方式继承后，在原基类为public,protectedc,private的成员在继承类里类型为表格里内容

class base
{
  public:
    std::string testPublic()
    {
      return std::string("this is public base");
    }
  protected:
    std::string testProtected()
    {
      return std::string("this is protected base");
    }
  private:
    std::string testPrivate()
    {
      return std::string("this is private base");
    }
};

class derivedPublic:public base
{
  public:
    std::string testPubPublic()
    {
      return testPublic()+= "in derived";
    }
    
    std::string testProPublic()
    {  
      return testProtected()+= "in derived";
    }
    
    std::string testPriPublic()   
    {  
      return testPrivate()+= "in derived";
    }
};

int main(int argc,char* argv[])
｛
  derivedPublic dpub;
  std::cout << dpub.testPublic() << std::endl; 
｝

报下面错误，说明testPrivate()不是derived私有函数而是base的私有函数

derived11.cpp:16: error: `std::string base::testPrivate()' is private
derived11.cpp:36: error: within this context


这样验证private类型成员无法被继承（public,private,protected）注：private，protected略去不做证明
下面只要验证 testProtected 能被第三层继承类继承，但是无法被第三层类直接调用就说明是public继承后继承类型为protected，而基类为Public类型成员则即可被继承又可以直接调用。

#include 
#include 

class base
{
  public:
    std::string testPublic()
    {
      return std::string("this is public base");
    }
  protected:
    std::string testProtected()
    {
      return std::string("this is protected base");
    }
  private:
    std::string testPrivate()
    {
      return std::string("this is private base");
    }
};

class derivedPublic:public base
{
  public:
    std::string testPubPublic()
    {
      return testPublic()+= "in derived";
    }
    
    std::string testProPublic()
    {  
      return testProtected()+= "in derived";
    }
    
//    std::string testPriPublic()   
//    {  
//      return testPrivate()+= "in derived";
//    }
};

class deepDerived:public derivedPublic
{
  public:
    std::string deepProtected()
    {
      return testProtected() +="in deep";
    }
    
    std::string deepPublic()
    {
      return testPublic() +="indeep";
    }
};

int main(int argc,char* argv[])
{
  derivedPublic dpub;
  std::cout << dpub.testProtected() << std::endl; 
  deepDerived deepdpub;
  std::cout<

这里服务器报错

derived12.cpp:13: error: `std::string base::testProtected()' is protected
derived12.cpp:62: error: within this context


这样就验证了一个是public，一个是protected，protected是不能直接调用的，但是被继承后是可以被public成员调用的。

下面的已经证明，详细步骤就略去如果对该部分验证感兴趣，可以看下面代码。



#include 
#include 
class base
{
  public:
    std::string testPublic()
    {
      return std::string("this is public base");
    }
  protected:
    std::string testProtected()
    {
      return std::string("this is protected base");
    }
  private:
    std::string testPrivate()
    {
      return std::string("this is private base");
    }
};

class derivedPublic:public base
{
  public:
    std::string testPubPublic()
    {
      return testPublic()+= "in derived";
    }
    
    std::string testProPublic()
    {  
      return testProtected()+= "in derived";
    }
    
//    std::string testPriPublic()   //私有成员并没有被继承下来
//    {  
//      return testPrivate()+= "in derived";
//    }
};

class deepDerived:public derivedPublic
{
  public:
    std::string test()
    {
      return testPublic() +="in 3";
    }
};

class derivedProtected:protected base
{
  public:
    std::string testPubProtected()
    {
      return testPublic()+= "in derived";
    }
    
    std::string testProProtected()
    {  
      return testProtected()+= "in derived";
    }
};

class deepDerived2:public derivedProtected
{
  public:
    std::string test()
    {
      return testPublic() +="in 3";
    }
};

class derivedPrivate:private base
{
  public:
    std::string testPubPirvate()
    {
      return testPublic()+= "in derived";
    }
    
    std::string testProPrivate()
    {  
      return testProtected()+= "in derived";
    }
    
};

//class deepDerived3:public derivedPrivate
//{
//  public:
//    std::string test()
//    {
//      return testPublic() +="in 3";
//    }
//};

int main(int argc,char* argv[])
{
  derivedPublic dpub;
  //derivedProtected dpro;
  //derivedPrivate dpri;
  std::cout<

以上就是对C++ j继承的资料整理，后续继续补充相关资料，谢谢大家对本站的支持！