entt/test/example/entity_copy.cpp

#include <gtest/gtest.h>
#include <entt/entity/registry.hpp>

TEST(Example, EntityCopy) {
    using namespace entt::literals;

    entt::registry registry{};
    auto &&custom = registry.storage<double>("custom"_hs);

    const auto src = registry.create();
    const auto dst = registry.create();
    const auto other = registry.create();

    custom.emplace(src, 1.);
    registry.emplace<int>(src, 42);
    registry.emplace<char>(src, 'c');
    registry.emplace<double>(other, 3.);

    ASSERT_TRUE(custom.contains(src));
    ASSERT_FALSE(registry.all_of<double>(src));
    ASSERT_TRUE((registry.all_of<int, char>(src)));
    ASSERT_FALSE((registry.any_of<int, char, double>(dst)));
    ASSERT_FALSE(custom.contains(dst));

    registry.visit([src, dst](auto &&storage) {
        // discard chars because why not, this is just an example after all
        if(storage.type() != entt::type_id<char>() && storage.contains(src)) {
            storage.emplace(dst, storage.get(src));
        }
    });

    ASSERT_TRUE((registry.all_of<int>(dst)));
    ASSERT_FALSE((registry.any_of<char, double>(dst)));
    ASSERT_TRUE(custom.contains(dst));

    ASSERT_EQ(registry.get<int>(dst), 42);
    ASSERT_EQ(custom.get(dst), 1.);
}