How can I iterate through the members of structs and classes in C ?-C++-php.cn

How can I iterate through the members of structs and classes in C ?

Barbara Streisand

Release： 2024-10-30 06:48:02

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How can I iterate through the members of structs and classes in C ?

Iterative Exploration of Struct and Class Members

C offers various methods for iterating through the members of structs and classes, enabling in-depth exploration of their internal elements.

REFLECTABLE Macro for Structured Retrieval

One technique involves utilizing the REFLECTABLE macro. By incorporating REFLECTABLE into the struct definition, as shown below, the fields become accessible for interrogation:

<code class="cpp">struct A
{
    REFLECTABLE
    (
        (int) a,
        (int) b,
        (int) c
    )
};</code>

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Utilizing this macro, you can traverse each field and print its value:

<code class="cpp">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);</code>

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Adapting Structs as Fusion Sequences

Alternatively, you can adapt structs as fusion sequences using Boost.Fusion. Here's an example:

<code class="cpp">struct A
{
    int a;
    int b;
    int c;
};

BOOST_FUSION_ADAPT_STRUCT
(
    A,
    (int, a)
    (int, b)
    (int, c)
)</code>

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Similar to the REFLECTABLE method, you can print the fields:

<code class="cpp">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));
}</code>

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