为什么'的boost :: any`比`无效*`好？ [英] Why is `boost::any` better than `void*`?

问题描述

什么先天的优势做的boost ::任何和的boost :: any_cast 提供超过使用无效* 和的dynamic_cast ？

What inherent advantages do boost::any and boost::any_cast offer over using void* and dynamic_cast?

推荐答案

的优点是，的boost ::任何是方式更加类型安全比无效* 。

The advantage is that boost::any is way more type-safe than void*.

例如

int i = 5;
void* p = &i;
static_cast<double*>(p);  //Compiler doesn't complain. Undefined Behavior.
boost::any a;
a = i;
boost::any_cast<double>(a); //throws, which is good

至于你的评论，你不能的dynamic_cast 从无效* 。您可以的dynamic_cast 仅从指针和引用其中至少有一个虚函数类类型（又名多态类型）

As to your comment, you cannot dynamic_cast from a void*. You can dynamic_cast only from pointers and references to class types which have at least one virtual function (aka polymorphic types)

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