aggregate_reflection.cpp

Inspect aggregate members by name, count, and reference. Demonstrates member counting, compile-time member-name lookup, mutable member access, and aggregate traversal with for_each_member.

#include <string_view>
 
#include <gmp/gmp.hpp>
 
struct Person {
    int age;
    double score;
};
 
int main() {
    Person person{42, 98.5};
    bool visited_age = false;
    bool visited_score = false;
 
    static_assert(gmp::member_count<Person>() == 2);
    static_assert(gmp::member_name<0, Person>() == "age");
    static_assert(gmp::member_name<1, Person>() == "score");
 
    auto& age = gmp::member_ref<0>(person);
    age += 1;
 
    gmp::for_each_member(person, [&](std::string_view name, auto& value) {
        if (name == "age") {
            visited_age = true;
            value += 1;
        } else if (name == "score") {
            visited_score = true;
        }
    });
 
    return (person.age == 44 && visited_age && visited_score) ? 0 : 1;
}