Iterating Over Struct and Class Members

In C , it is possible to iterate through the members of a struct or class to retrieve their names and values. Here are a few approaches to achieve this:

Using Macros

The REFLECTABLE macro can be used to define structs that allow for introspection. The macro defines the members of the struct as a comma-separated list of type-name pairs. For example:

struct A
{
    REFLECTABLE
    (
        (int) a,
        (int) b,
        (int) c
    )
};

Once the struct is defined, you can use a visitor function to iterate over its members and print their names and values:

struct print_visitor
{
    template
    void operator()(FieldData f)
    {
        std::cout 
void print_fields(T & x)
{
    visit_each(x, print_visitor());
}

A x;
print_fields(x);

Adapting Structs as Fusion Sequences

Another approach is to adapt the struct as a fusion sequence using the BOOST_FUSION_ADAPT_STRUCT macro. This macro defines the struct members as a sequence of elements with the corresponding type and value. For example:

struct A
{
    int a;
    int b;
    int c;
};

BOOST_FUSION_ADAPT_STRUCT
(
    A,
    (int, a)
    (int, b)
    (int, c)
)

Once the struct is adapted, you can use a range loop to iterate over the members and print their names and values:

struct print_visitor
{
    template
    void operator()(Index, C & c)
    {
        std::cout ::call() 
                  (c) 
                  
void print_fields(C & c)
{
    typedef boost::mpl::range_c::type::value> range;
    boost::mpl::for_each(boost::bind(print_visitor(), boost::ref(c), _1));
}

Both these approaches allow you to introspect structs and classes, providing access to their members and their values at runtime.