dynamic_cast of void * [英] dynamic_cast of void *

问题描述

我需要使用动态转换void *

I need to use dynamic cast void*

void *target = (MYClass*)target;//I am storing initially(to implment delegate mechanism)
....
delegateClass *delegate = dynamic_cast<delegateClass*>(target);

这是给错误不能转换void *，我不能使用下面的代码...因为它是一个委托机制

It is giving error cannot convert void*, I cannot use below code... since it is a delegate mechanism

delegateClass *delegate = dynamic_cast<delegateClass*>(((MYClass*))target);

如何获取目标类型和实现...如果我使用typeid类的名称，但是如何在上面的方程中使用typeid而不是（（（MYClass *））target）。

How to get the type of target and implement... If i use typeid() i can get the name of the class but how to use typeid in the above equation instead of (((MYClass*))target).

推荐答案

除非变量的原始类型有一个vtable（即，有虚函数），否则不能使用动态转换。这是因为dynamic_cast需要运行时类型信息，它记录在vtable中;如果vtable缺失，编译器不知道对象是什么类型。

You cannot use dynamic cast unless the original type of the variable had a vtable (ie, had virtual functions). This is because dynamic_cast requires run-time type information, which is recorded in the vtable; if the vtable is missing, the compiler doesn't know what type the object is.

你应该声明一个带有虚拟析构函数的基类，并使用指向这个基类的指针而不是 void * 。

You should declare a base class with a virtual destructor, and use pointers to this base class rather than void *.

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