refactor(core): add FieldTrait::{View, ConstView}

core/include/cubos/core/reflection/traits/fields.hpp

@@ -34,6 +34,12 @@ namespace cubos::core::reflection
         /// @brief Used to iterate over the fields on a fields trait.
         class Iterator;
 
+        /// @brief Provides mutable access to an object.
+        class View;
+
+        /// @brief Provides immutable access to an object.
+        class ConstView;
+
         ~FieldsTrait();
 
         /// @brief Constructs.
@@ -76,6 +82,14 @@ namespace cubos::core::reflection
         /// @return Iterator.
         static Iterator end();
 
+        /// @brief Returns a view of the given object instance.
+        /// @param instance Object instance.
+        /// @return Object view.
+        View view(void* instance) const;
+
+        /// @copydoc view(void*) const
+        ConstView view(const void* instance) const;
+
     private:
         Field* mFirstField{nullptr};
         Field* mLastField{nullptr};
@@ -132,6 +146,15 @@ namespace cubos::core::reflection
         /// @return Name of the field.
         const std::string& name() const;
 
+        /// @brief Returns the next field in the linked list.
+        /// @return Pointer to next field or null if this is the last field.
+        const Field* next() const;
+
+    private:
+        friend FieldsTrait;
+        friend View;
+        friend ConstView;
+
         /// @brief Returns the address of the field on a given instance.
         /// @param instance Pointer to the instance.
         /// @return Address of the field on the given instance.
@@ -145,13 +168,6 @@ namespace cubos::core::reflection
         /// @copydoc pointerTo(void*)
         const void* pointerTo(const void* instance) const;
 
-        /// @brief Returns the next field in the linked list.
-        /// @return Pointer to next field or null if this is the last field.
-        const Field* next() const;
-
-    private:
-        friend FieldsTrait;
-
         const Type& mType;
         std::string mName;
         AddressOf* mAddressOf;
@@ -191,4 +207,162 @@ namespace cubos::core::reflection
     private:
         const Field* mField;
     };
+
+    class FieldsTrait::View
+    {
+    public:
+        /// @brief Used to iterate over the fields of an object.
+        class Iterator;
+
+        /// @brief Constructs.
+        /// @param trait Trait.
+        /// @param instance Instance.
+        View(const FieldsTrait& trait, void* instance);
+
+        /// @brief Gets a pointer to the value of the given field on the object.
+        /// @param field Field.
+        /// @return Field value.
+        void* get(const Field& field) const;
+
+        /// @brief Gets an iterator to the first field.
+        /// @return Iterator.
+        Iterator begin() const;
+
+        /// @brief Gets an iterator to the field after the last field.
+        /// @return Iterator.
+        Iterator end() const;
+
+    private:
+        const FieldsTrait& mTrait;
+        void* mInstance;
+    };
+
+    class FieldsTrait::ConstView
+    {
+    public:
+        /// @brief Used to iterate over the fields of an object.
+        class Iterator;
+
+        /// @brief Constructs.
+        /// @param trait Trait.
+        /// @param instance Instance.
+        ConstView(const FieldsTrait& trait, const void* instance);
+
+        /// @brief Gets a pointer to the value of the given field on the object.
+        /// @param field Field.
+        /// @return Field value.
+        const void* get(const Field& field) const;
+
+        /// @brief Gets an iterator to the first field.
+        /// @return Iterator.
+        Iterator begin() const;
+
+        /// @brief Gets an iterator to the field after the last field.
+        /// @return Iterator.
+        Iterator end() const;
+
+    private:
+        const FieldsTrait& mTrait;
+        const void* mInstance;
+    };
+
+    class FieldsTrait::View::Iterator
+    {
+    public:
+        /// @brief Output structure for the iterator.
+        struct Output
+        {
+            const Field* field; ///< Field.
+            void* value;        ///< Value.
+        };
+
+        /// @brief Constructs.
+        /// @param view View.
+        /// @param field Field.
+        Iterator(const View& view, const Field* field);
+
+        /// @brief Copy constructs.
+        /// @param other Other iterator.
+        Iterator(const Iterator& other) = default;
+
+        /// @brief Compares two iterators.
+        /// @param other Other iterator.
+        /// @return Whether the iterators point to the same field.
+        bool operator==(const Iterator& other) const;
+
+        /// @brief Compares two iterators.
+        /// @param other Other iterator.
+        /// @return Whether the iterators point to different fields.
+        bool operator!=(const Iterator& /*other*/) const;
+
+        /// @brief Accesses the field referenced by this iterator.
+        /// @note Aborts if out of bounds.
+        /// @return Output.
+        const Output& operator*() const;
+
+        /// @brief Accesses the field referenced by this iterator.
+        /// @note Aborts if out of bounds.
+        /// @return Output.
+        const Output* operator->() const;
+
+        /// @brief Advances the iterator.
+        /// @note Aborts if out of bounds.
+        /// @return Reference to this.
+        Iterator& operator++();
+
+    private:
+        void* mInstance;
+        const Field* mField;
+        mutable Output mOutput;
+    };
+
+    class FieldsTrait::ConstView::Iterator
+    {
+    public:
+        /// @brief Output structure for the iterator.
+        struct Output
+        {
+            const Field* field; ///< Field.
+            const void* value;  ///< Value.
+        };
+
+        /// @brief Constructs.
+        /// @param view View.
+        /// @param field Field.
+        Iterator(const ConstView& view, const Field* field);
+
+        /// @brief Copy constructs.
+        /// @param other Other iterator.
+        Iterator(const Iterator& other) = default;
+
+        /// @brief Compares two iterators.
+        /// @param other Other iterator.
+        /// @return Whether the iterators point to the same field.
+        bool operator==(const Iterator& other) const;
+
+        /// @brief Compares two iterators.
+        /// @param other Other iterator.
+        /// @return Whether the iterators point to different fields.
+        bool operator!=(const Iterator& /*other*/) const;
+
+        /// @brief Accesses the field referenced by this iterator.
+        /// @note Aborts if out of bounds.
+        /// @return Output.
+        const Output& operator*() const;
+
+        /// @brief Accesses the field referenced by this iterator.
+        /// @note Aborts if out of bounds.
+        /// @return Output.
+        const Output* operator->() const;
+
+        /// @brief Advances the iterator.
+        /// @note Aborts if out of bounds.
+        /// @return Reference to this.
+        Iterator& operator++();
+
+    private:
+        const void* mInstance;
+        const Field* mField;
+        mutable Output mOutput;
+    };
 } // namespace cubos::core::reflection

core/samples/reflection/traits/fields/main.cpp

@@ -48,7 +48,7 @@ int main()
 
     /// [Accessing fields by name]
     Person person{.age = 21, .weight = 68.4F};
-    *static_cast<float*>(fields.field("weight")->pointerTo(&person)) += 20.0F;
+    *static_cast<float*>(fields.view(&person).get(*fields.field("weight"))) += 20.0F;
     CUBOS_INFO("New weight: {}", person.weight); // 88.4
 }
 /// [Accessing fields by name]

core/src/cubos/core/reflection/traits/fields.cpp

@@ -133,3 +133,127 @@ FieldsTrait::Iterator FieldsTrait::end()
 {
     return Iterator{nullptr};
 }
+
+FieldsTrait::View FieldsTrait::view(void* instance) const
+{
+    return View{*this, instance};
+}
+
+FieldsTrait::ConstView FieldsTrait::view(const void* instance) const
+{
+    return ConstView{*this, instance};
+}
+
+FieldsTrait::View::View(const FieldsTrait& trait, void* instance)
+    : mTrait{trait}
+    , mInstance{instance}
+{
+}
+
+void* FieldsTrait::View::get(const Field& field) const
+{
+    return field.pointerTo(mInstance);
+}
+
+FieldsTrait::View::Iterator FieldsTrait::View::begin() const
+{
+    return Iterator{*this, mTrait.mFirstField};
+}
+
+FieldsTrait::View::Iterator FieldsTrait::View::end() const
+{
+    return Iterator{*this, nullptr};
+}
+
+FieldsTrait::ConstView::ConstView(const FieldsTrait& trait, const void* instance)
+    : mTrait{trait}
+    , mInstance{instance}
+{
+}
+
+const void* FieldsTrait::ConstView::get(const Field& field) const
+{
+    return field.pointerTo(mInstance);
+}
+
+FieldsTrait::ConstView::Iterator FieldsTrait::ConstView::begin() const
+{
+    return Iterator{*this, mTrait.mFirstField};
+}
+
+FieldsTrait::ConstView::Iterator FieldsTrait::ConstView::end() const
+{
+    return Iterator{*this, nullptr};
+}
+
+FieldsTrait::View::Iterator::Iterator(const View& view, const Field* field)
+    : mInstance{view.mInstance}
+    , mField{field}
+{
+}
+
+bool FieldsTrait::View::Iterator::operator==(const Iterator& other) const
+{
+    return mInstance == other.mInstance && mField == other.mField;
+}
+
+bool FieldsTrait::View::Iterator::operator!=(const Iterator& other) const
+{
+    return !(*this == other);
+}
+
+const FieldsTrait::View::Iterator::Output& FieldsTrait::View::Iterator::operator*() const
+{
+    CUBOS_ASSERT(mField != nullptr, "Iterator out of bounds");
+    mOutput.field = mField;
+    mOutput.value = mField->pointerTo(mInstance);
+    return mOutput;
+}
+
+const FieldsTrait::View::Iterator::Output* FieldsTrait::View::Iterator::operator->() const
+{
+    return &this->operator*();
+}
+
+FieldsTrait::View::Iterator& FieldsTrait::View::Iterator::operator++()
+{
+    CUBOS_ASSERT(mField != nullptr, "Iterator out of bounds");
+    mField = mField->next();
+    return *this;
+}
+
+FieldsTrait::ConstView::Iterator::Iterator(const ConstView& view, const Field* field)
+    : mInstance{view.mInstance}
+    , mField{field}
+{
+}
+
+bool FieldsTrait::ConstView::Iterator::operator==(const Iterator& other) const
+{
+    return mInstance == other.mInstance && mField == other.mField;
+}
+
+bool FieldsTrait::ConstView::Iterator::operator!=(const Iterator& other) const
+{
+    return !(*this == other);
+}
+
+const FieldsTrait::ConstView::Iterator::Output& FieldsTrait::ConstView::Iterator::operator*() const
+{
+    CUBOS_ASSERT(mField != nullptr, "Iterator out of bounds");
+    mOutput.field = mField;
+    mOutput.value = mField->pointerTo(mInstance);
+    return mOutput;
+}
+
+const FieldsTrait::ConstView::Iterator::Output* FieldsTrait::ConstView::Iterator::operator->() const
+{
+    return &this->operator*();
+}
+
+FieldsTrait::ConstView::Iterator& FieldsTrait::ConstView::Iterator::operator++()
+{
+    CUBOS_ASSERT(mField != nullptr, "Iterator out of bounds");
+    mField = mField->next();
+    return *this;
+}

core/tests/reflection/traits/fields.cpp

@@ -37,12 +37,13 @@ TEST_CASE("reflection::FieldsTrait")
         const auto* field = fields.field("foo");
         REQUIRE(field != nullptr);
         CHECK(field == &*fields.begin());
+        CHECK(fields.begin() != fields.end());
         CHECK(++fields.begin() == fields.end());
 
         ObjectType object{};
         CHECK(field->name() == "foo");
         CHECK(field->type().is<SimpleType>());
-        CHECK(field->pointerTo(&object) == &object.foo);
+        CHECK(fields.view(&object).get(*field) == &object.foo);
     }
 
     SUBCASE("two fields")
@@ -61,9 +62,9 @@ TEST_CASE("reflection::FieldsTrait")
         ObjectType object{};
         CHECK(fooField->name() == "foo");
         CHECK(fooField->type().is<SimpleType>());
-        CHECK(fooField->pointerTo(&object) == &object.foo);
+        CHECK(fields.view(&object).get(*fooField) == &object.foo);
         CHECK(barField->name() == "bar");
         CHECK(barField->type().is<SimpleType>());
-        CHECK(barField->pointerTo(static_cast<const ObjectType*>(&object)) == &object.bar);
+        CHECK(fields.view(static_cast<const ObjectType*>(&object)).get(*barField) == &object.bar);
     }
 }