entt/test/example/custom_identifier.cpp

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

struct entity_id {
    using entity_type = std::uint32_t;
    static constexpr auto null = entt::null;

    constexpr entity_id(entity_type value = null) ENTT_NOEXCEPT
        : entt{value} {}

    constexpr entity_id(const entity_id &other) ENTT_NOEXCEPT
        : entt{other.entt} {}

    constexpr operator entity_type() const ENTT_NOEXCEPT {
        return entt;
    }

private:
    entity_type entt;
};

TEST(Example, CustomIdentifier) {
    entt::basic_registry<entity_id> registry{};
    entity_id entity{};

    ASSERT_FALSE(registry.valid(entity));
    ASSERT_TRUE(entity == entt::null);

    entity = registry.create();

    ASSERT_TRUE(registry.valid(entity));
    ASSERT_TRUE(entity != entt::null);

    ASSERT_FALSE((registry.all_of<int, char>(entity)));
    ASSERT_EQ(registry.try_get<int>(entity), nullptr);

    registry.emplace<int>(entity, 42);

    ASSERT_TRUE((registry.any_of<int, char>(entity)));
    ASSERT_EQ(registry.get<int>(entity), 42);

    registry.destroy(entity);

    ASSERT_FALSE(registry.valid(entity));
    ASSERT_TRUE(entity != entt::null);

    entity = registry.create();

    ASSERT_TRUE(registry.valid(entity));
    ASSERT_TRUE(entity != entt::null);
}