C/C++ 公有继承、保护继承和私有继承的对比详解

#include <iostream> 

class Base { 
public: 
  int public_a; 
  virtual void test() = 0; 

protected: 
  int protected_a; 

private: 
  int private_a; 
}; 

//公有继承 
class PublicDerived : public Base { 
public: 
  virtual void test() { 
    public_a = 1;          //public_a public继承后还是public类型 
    protected_a = 2;        //protected_a 还是protected类型 
    //private_a = 3;         //派生类不可访问基类私有成员 
  } 
}; 

//保护继承 
class ProtectedDerived : protected Base { 
public: 
  virtual void test() { 
    public_a = 1;          //public_a protected继承后变为protected类型 
    protected_a = 2;        //protected_a 还是protected类型 
    //private_a = 3;        //派生类不可访问基类私有成员 
  } 
}; 

//私有继承 
class PrivateDerived : private Base { 
public: 
  virtual void test() { 
    public_a = 1;          //public_a private继承后变为private类型 
    protected_a = 2;        //protected_a private继承后变为private类型 
    //private_a = 3;        //派生类不可访问基类私有成员 
  } 
}; 

#include <iostream> 

class Person { 
public: 
  Person(){}; 

  void eat() {std::cout << "eat\n";} 
}; 

//公有继承 
class PublicStudent : public Person { 
public: 
  PublicStudent() {} 

  void study() {std::cout << "study\n";} 
}; 

//保护继承 
class ProtectedStudent : protected Person { 
public: 
  ProtectedStudent() {} 

  void study() {std::cout << "study\n";} 
}; 

//私有继承 
class PrivateStudent : private Person { 
public: 
  PrivateStudent() {} 

  void study() {std::cout << "study\n";} 
}; 

 

void func_test(Person &p) { 
  p.eat(); 
} 

int main() { 

  PublicStudent public_s; 
  ProtectedStudent protected_s; 
  PrivateStudent private_s; 

  func_test(public_s);          //正确，公有继承时，派生类可以做基类的所有事情 
  func_test(protected_s);         //出错，保护继承时，派生类不能做基类的所有事情 
  func_test(private_s);          //出错，私有继承时，派生类不可以做基类的所有事情 

  system("pause"); 

  return 0; 
}