找出 C++ 空指针的类型

2021-12-31 00:00:00 casting c++ void-pointers

我有一个小问题:如何找出 C++ 指针的类型?

I have a small question: how do I find out what type a C++ pointer is?

我经常在我的控制台程序中使用一个小函数来收集输入，它看起来像这样:

I often use a small function in my console programs to gather input, which looks something like this:

void query(string what-to-ask, [insert datatype here] * input)

我想创建一个通用表单，使用一个空指针，但我不能创建一个空指针，那么我如何找出它的类型以便我可以转换它?

I would like to create a generic form, using a void pointer, but I can't cin a void pointer, so how to I find out it's type so I can cast it?

推荐答案

你不能.

然而，一种替代方法是取消空指针，让所有东西都派生自一个公共基类并使用 RTTI.

However, one alternative is to do away with void pointers, make everything derive from a common base class and use RTTI.

示例:

class Base
{
public:
   virtual ~Base() {}
};

class Foo : public Base { /* ... */ };

void SomeFunction(Base *obj)
{
    Foo *p = dynamic_cast<Foo*>(obj);
    if (p)
    {
        // This is of type Foo, do something with it...
    }
}

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