new meta_poly_ptr method in META_HPP_ENABLE_POLY_INFO macro

ROADMAP.md

@@ -3,6 +3,7 @@
 ## Backlog
 
 - add coverage information
+- add an ucast function with a dynamic `to` argument
 
 ## Version 1.0
 

develop/manuals/meta_examples/ucast_example.cpp

@@ -18,11 +18,15 @@ namespace
     // like `ucast` or `resolve_type(T&&)`
 
     struct A {
+        A() = default;
+        A(const A&) = default;
         virtual ~A() = default;
         META_HPP_ENABLE_POLY_INFO()
     };
 
     struct B {
+        B() = default;
+        B(const B&) = default;
         virtual ~B() = default;
         META_HPP_ENABLE_POLY_INFO()
     };

develop/singles/headers/meta.hpp/meta_all.hpp

@@ -4679,6 +4679,12 @@ public: \
     META_HPP_ENABLE_BASE_INFO(__VA_ARGS__) \
 public: \
     META_HPP_DETAIL_IGNORE_OVERRIDE_WARNINGS_PUSH() \
+    virtual ::meta_hpp::uvalue meta_poly_ptr() { \
+        return ::meta_hpp::uvalue{this}; \
+    } \
+    virtual ::meta_hpp::uvalue meta_poly_ptr() const { \
+        return ::meta_hpp::uvalue{this}; \
+    } \
     virtual ::meta_hpp::detail::poly_info meta_poly_info(::meta_hpp::detail::type_registry& registry) const { \
         using self_type = std::remove_cvref_t<decltype(*this)>; \
         return ::meta_hpp::detail::poly_info{.ptr = this, .type = registry.resolve_by_type<self_type>()}; \

develop/untests/meta_issues/github_discussion_88.cpp

@@ -0,0 +1,74 @@
+/*******************************************************************************
+ * This file is part of the "https://github.com/blackmatov/meta.hpp"
+ * For conditions of distribution and use, see copyright notice in LICENSE.md
+ * Copyright (C) 2021-2024, by Matvey Cherevko (blackmatov@gmail.com)
+ ******************************************************************************/
+
+#include <meta.hpp/meta_all.hpp>
+#include <doctest/doctest.h>
+
+namespace
+{
+    struct component {
+        component() = default;
+        component(const component&) = default;
+        virtual ~component() = default;
+        META_HPP_ENABLE_POLY_INFO()
+    };
+
+    struct position_component : component {
+        META_HPP_ENABLE_POLY_INFO()
+    public:
+        explicit position_component(int nx, int ny) : x{nx}, y{ny} {}
+
+        int x{};
+        int y{};
+    };
+}
+
+TEST_CASE("meta/meta_discussion/88") {
+    namespace meta = meta_hpp;
+
+    meta::class_<position_component>()
+        .member_("x", &position_component::x, meta::member_policy::as_pointer)
+        .member_("y", &position_component::y, meta::member_policy::as_pointer);
+
+    position_component position{21, 42};
+
+    std::vector<component*> components{&position};
+
+    for (component* c : components) {
+        // meta_poly_ptr returns a pointer of the most derived type (position_component* in this case)
+        meta::uvalue derived_instance_ptr = c->meta_poly_ptr();
+        meta::any_type derived_instance_ptr_type = derived_instance_ptr.get_type();
+        CHECK(derived_instance_ptr_type == meta::resolve_type<position_component*>());
+
+        // to get all members of the component we should extract a class type from the pointer (position_component)
+        meta::any_type derived_instance_type = derived_instance_ptr_type.as_pointer().get_data_type();
+        CHECK(derived_instance_type == meta::resolve_type<position_component>());
+
+        // for each member we can show our debug inspector (imgui input for example)
+        for (const meta::member& m : derived_instance_type.as_class().get_members()) {
+            // we registered members as pointers (member_policy::as_pointer), so the type of the member is a pointer
+            CHECK(m.get_type() == meta::resolve_type<int position_component::*>());
+            CHECK(m.get_type().get_value_type() == meta::resolve_type<int>());
+
+            // Note:
+            // We can register members without any policy then member::get will return copy of this member value,
+            // and to change this member we will have to call member::set function.
+            // But in this case we will change values in-place by a pointer
+
+            meta::uvalue value = m.get(derived_instance_ptr);
+            CHECK(value.get_type() == meta::resolve_type<int*>());
+
+            int* raw_value = value.as<int*>();
+
+            // here we can show the value on the screen or change it
+            CHECK((*raw_value == 21 || *raw_value == 42));
+            *raw_value = 84;
+        }
+
+        CHECK(position.x == 84);
+        CHECK(position.y == 84);
+    }
+}

develop/untests/meta_types/poly_resolving2_tests.cpp

@@ -13,6 +13,8 @@ namespace
     struct derived : base {};
 
     struct poly_base {
+        poly_base() = default;
+        poly_base(const poly_base&) = default;
         virtual ~poly_base() = default;
         META_HPP_ENABLE_POLY_INFO()
     };

develop/untests/meta_types/poly_resolving_tests.cpp

@@ -9,6 +9,8 @@
 
 namespace {
     struct A {
+        A() = default;
+        A(const A&) = default;
         virtual ~A() = default;
         META_HPP_ENABLE_POLY_INFO()
     };

headers/meta.hpp/meta_detail/base_info.hpp

@@ -8,6 +8,7 @@
 
 #include "../meta_base.hpp"
 #include "../meta_types.hpp"
+#include "../meta_uvalue.hpp"
 
 #include "type_registry.hpp"
 
@@ -45,6 +46,12 @@ public: \
     META_HPP_ENABLE_BASE_INFO(__VA_ARGS__) \
 public: \
     META_HPP_DETAIL_IGNORE_OVERRIDE_WARNINGS_PUSH() \
+    virtual ::meta_hpp::uvalue meta_poly_ptr() { \
+        return ::meta_hpp::uvalue{this}; \
+    } \
+    virtual ::meta_hpp::uvalue meta_poly_ptr() const { \
+        return ::meta_hpp::uvalue{this}; \
+    } \
     virtual ::meta_hpp::detail::poly_info meta_poly_info(::meta_hpp::detail::type_registry& registry) const { \
         using self_type = std::remove_cvref_t<decltype(*this)>; \
         return ::meta_hpp::detail::poly_info{.ptr = this, .type = registry.resolve_by_type<self_type>()}; \