访问指向其基类的指针所指向的派生类对象的成员变量 [英] Access member variables of derived class object pointed to by a pointer to its base class

问题描述

我有一个基类和两个从它派生的类.我在基类中有几个虚函数，因此我创建了一个指向基类的指针，并使用该指针访问这些方法.

I have one base class and two classes derived from it. I have several virtual functions in the base class so I create a pointer to the base class and use this pointer to access these methods.

现在，我想使用指向派生类对象的基类的指针访问派生类的成员变量(该变量在基类中不存在).

Now I want to access member variable of derived class (this variable is not present in the base class) using the pointer to base class which points to a derived class object.

可以做到吗?应该这样做吗?

推荐答案

为什么要访问派生类的界面?使用多态时，您无需关心基类引用/指针背后的内容. 如果这样做，通常就暗示了设计缺陷.

Why do you want to access the derived class' interface? When you use polymorphism, you shouldn't need to care about what's behind a base class reference/pointer. If you do, then that's usually a hint at a design flaw.

您要尝试的是开机类型". (如果B*后面是D1对象，则执行此操作，否则执行该操作.")接通类型正在规避多态性和不良信号.

What you are trying to do is a "switch-on-type". ("If behind B* is a D1 object, do this, otherwise do that".) A switch-on-type is circumventing polymorphism and a bad sign.

注意:有一种方法可以执行此操作(dynamic_cast)，但是由于上述原因，我认为这是一种不好的做法，因此不再赘述.

Note: There is a way to do this (dynamic_cast), but for the reasons mentioned above I consider this bad practice and won't elaborate on it.

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