使用“公共”在派生类声明中？ [英] Use of "Public" in a derived class declaration?

问题描述

给定此基类：

  class Employee 
 {
 char * name; 
 int age 
 
 public：
 Employee（char * name）; 
 void print（）; 
}; 
  

对于public，这之间有什么区别：

 类经理：public Employee 
 {
 EmployeeList employees; 
 
 public：
 Manager（char * name，Employee * people）; 
 void print（）; 
}; 
  

并且：

  class Manager：Employee 
 {
 EmployeeList employees; 
 
 public：
 Manager（char * name，Employee * people）; 
 void print（）; 
}; 
  

解决方案

默认是私有继承。以此为例：

  class B {}; 
 class D：B {}; 
  

使用私有继承作为默认值。这意味着D得到B拥有的所有受保护和公共字段和方法（如果我们实际上声明任何），但不能转换为B.因此，此代码失败：

  void foo（B * argument）{} 
 foo（new D）; //不允许
  

如果D从B公开继承，那么D可以转换为B，

第二个区别是B中的所有受保护和公共成员都成为D中的私有成员 / p>

这是什么意思？公共继承意味着D IS_A B，但私有继承意味着以...实现。从B继承D意味着你想利用B中的一些功能，但不是因为D IS_A B，或者因为B和D之间有任何概念上的连接：D

Given this base class:

class Employee
{
     char* name;
     int age;

  public:
     Employee(char* name);
     void print();
};

With regards to the "public", what's the difference between this:

class Manager : public Employee
{
   EmployeeList employees;

   public:
     Manager(char* name, Employee* people);
     void print();
};

and this:

class Manager : Employee
{
   EmployeeList employees;

  public:
     Manager(char* name, Employee* people);
     void print();
};

解决方案

The default is private inheritance. take this example:

class B { };
class D: B { };

uses private inheritance as its the default. This means that D gets all the protected and public fields and methods that B has (if we actually declared any), but can't be cast to a B. Therefore, this code fails:

void foo(B* argument) {}
foo(new D);                   //not allowed

If D publicly inherited from B, then a D could be cast to a B, and this function call would be fine.

The second difference is that all the protected and public members in B become private members in D.

What does this actually mean? Public inheritance means D IS_A B, but private inheritance means "is implemented in terms of". Inheriting D from B means you want to take advantage of some of the features in B, but not because D IS_A B or because there's any conceptual connection between B and D. :D

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