C ++模板元编程，成员变量数? [英] C++ template meta-programming, number of member variables?

问题描述

在C ++中是否可以确定泛型类中的变量/字段数? 例如

Is it possible in C++ to determine number of variables/fields in the generic class? for example

// suppose I need metaclass number_members determines number of members

struct example { int i, j; };
assert(number_members<example>::value==2);

我浏览了mpl，但找不到实现.

I looked through mpl but could not find implementation.

谢谢.

推荐答案

否. C ++不提供对结构的一般自省.

No. C++ does not provide general introspection into structures.

您可以尝试使用C ++ 0x std::tuple ，它具有常规POD struct的某些功能.或者，尝试从增强MPL 库.如果您刚开始使用C ++，那会有点先进.

You can try a C++0x std::tuple, which has some of the features of a general POD struct. Or, try to roll your own from the Boost MPL library. That would be a bit advanced if you're just getting started with C++.

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