问题描述
是否可以在 C++ 中遍历 Struct 或 Class 以找到其所有成员?例如,如果我有 struct a 和 class b:
Is it possible in C++ to iterate through a Struct or Class to find all of its members? For example, if I have struct a, and class b:
struct a
{
int a;
int b;
int c;
}
class b
{
public:
int a;
int b;
private:
int c;
}
是否可以循环它们说得到一个打印语句,说结构 a 具有名为 a、b、c 的 int"或b 类具有名为 a、b、c 的 int"
Would it be possible to loop them to say get a print statement saying "Struct a has int named a, b, c" or "Class b has int named a, b, c"
推荐答案
有几种方法可以做到这一点,但您需要使用一些宏来定义或调整结构.
There are a couple of ways to do this, but you need to use some macros to either define or adapt the struct.
您可以使用 this answer 中给出的 REFLECTABLE
宏来定义这样的结构:
You can use the REFLECTABLE
macro given in this answer to define the struct like this:
struct A
{
REFLECTABLE
(
(int) a,
(int) b,
(int) c
)
};
然后你可以遍历字段并像这样打印每个值:
And then you can iterate over the fields and print each value like this:
struct print_visitor
{
template<class FieldData>
void operator()(FieldData f)
{
std::cout << f.name() << "=" << f.get() << std::endl;
}
};
template<class T>
void print_fields(T & x)
{
visit_each(x, print_visitor());
}
A x;
print_fields(x);
另一种方法是将结构调整为融合序列(参见 文档).举个例子:
Another way is to adapt the struct as a fusion sequence (see the documentation). Here's an example:
struct A
{
int a;
int b;
int c;
};
BOOST_FUSION_ADAPT_STRUCT
(
A,
(int, a)
(int, b)
(int, c)
)
然后您也可以使用此打印字段:
Then you can print the fields as well using this:
struct print_visitor
{
template<class Index, class C>
void operator()(Index, C & c)
{
std::cout << boost::fusion::extension::struct_member_name<C, Index::value>::call()
<< "="
<< boost:::fusion::at<Index>(c)
<< std::endl;
}
};
template<class C>
void print_fields(C & c)
{
typedef boost::mpl::range_c<int,0, boost::fusion::result_of::size<C>::type::value> range;
boost::mpl::for_each<range>(boost::bind<void>(print_visitor(), boost::ref(c), _1));
}
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