added object_proxy as the holder of the object in object_ptr

include/matador/object/attribute_definition_generator.hpp

@@ -81,14 +81,23 @@ public:
 
   template<class Pointer>
   void on_belongs_to(const char *id, Pointer &x, const utils::foreign_attributes &/*attr*/) {
-    if (const auto result = determine_foreign_ref(std::type_index(typeid(typename Pointer::value_type)))) {
-      columns_.push_back(fk_column_generator_.generate(id, *x, *result));
-    }
+    on_foreign_key(id, x);
   }
   template<class Pointer>
   void on_has_one(const char *id, Pointer &x, const utils::foreign_attributes &/*attr*/) {
+    on_foreign_key(id, x);
+  }
+
+  template <class Pointer>
+  void on_foreign_key(const char *id, Pointer &x) {
     if (const auto result = determine_foreign_ref(std::type_index(typeid(typename Pointer::value_type)))) {
+      if (x.empty()) {
+        typename Pointer::value_type temp_val;
+        columns_.push_back(fk_column_generator_.generate(id, temp_val, *result));
+      } else {
         columns_.push_back(fk_column_generator_.generate(id, *x, *result));
+
+      }
     }
   }
   template<class ContainerType>

include/matador/object/object_proxy.hpp

@@ -9,17 +9,33 @@ class basic_object_proxy {
 public:
     virtual ~basic_object_proxy() = default;
 
-    virtual void *get() const = 0;
+    [[nodiscard]] virtual void *get() const = 0;
 };
 
 template<class Type>
 class object_proxy : public basic_object_proxy {
 public:
-    void *get() const override { return static_cast<Type *>(this)->get(); }
+    object_proxy() = default;
+    explicit object_proxy(Type* obj)
+    : obj_(obj) {}
+    explicit object_proxy(std::unique_ptr<Type> obj)
+    : obj_(std::move(obj)) {}
+
+    [[nodiscard]] void *get() const override { return static_cast<void*>(obj_.get()); }
 
     Type* operator->() const { return obj_.get(); }
+    Type& operator*() { return *obj_; }
+    const Type& operator*() const { return *obj_; }
+
+    Type* pointer() const { return obj_.get(); }
+
+    Type& ref() { return *obj_; }
+    const Type& ref() const { return *obj_; }
+
+    void reset(Type* obj) { obj_.reset(obj); }
+
 private:
-    std::shared_ptr<Type> obj_{};
+    std::unique_ptr<Type> obj_{};
 };
 
 }

include/matador/object/object_ptr.hpp

@@ -3,6 +3,7 @@
 
 #include "matador/utils/identifier.hpp"
 
+#include "matador/object/object_proxy.hpp"
 #include "matador/object/primary_key_resolver.hpp"
 
 #include <memory>
@@ -11,35 +12,36 @@ namespace matador::object {
 template <typename Type>
 class object_ptr {
 public:
-  object_ptr() = default;
+  object_ptr()
+  : ptr_(std::make_shared<object_proxy<Type>>()) {}
   explicit object_ptr(Type *obj)
-  : ptr_(obj)
+  : ptr_(std::make_shared<object_proxy<Type>>(obj))
   , pk_(primary_key_resolver::resolve_object(*obj).pk) {}
-  explicit object_ptr(std::shared_ptr<Type> obj) : ptr_(obj) {}
   object_ptr(const object_ptr &other) : ptr_(other.ptr_) {}
   object_ptr(object_ptr &&other) noexcept : ptr_(std::move(other.ptr_)) {}
   object_ptr &operator=(const object_ptr &other) = default;
   object_ptr &operator=(object_ptr &&other) = default;
 
   using value_type = Type;
-  Type* operator->() const { return ptr_.get(); }
-  Type& operator*() const { return *ptr_; }
+  Type* operator->() const { return ptr_->pointer(); }
+  Type& operator*() { return ptr_->ref(); }
+  const Type& operator*() const { return ptr_->ref(); }
 
-  [[nodiscard]] bool empty() const { return ptr_ == nullptr; }
+  [[nodiscard]] bool empty() const { return ptr_->pointer() == nullptr; }
   void reset(Type *obj) {
-    ptr_.reset(obj);
+    ptr_->reset(obj);
     pk_ = primary_key_resolver::resolve_object(*obj).pk;
   }
 
-  Type* get() { return ptr_.get(); }
-  const Type* get() const { return ptr_.get(); }
+  Type* get() const { return static_cast<Type*>(ptr_->pointer()); }
+
   operator bool() { return valid(); }
   bool valid() { return ptr_ != nullptr; }
 
   [[nodiscard]] const utils::identifier& primary_key() const { return pk_; }
   void primary_key(const utils::identifier &pk) { pk_ = pk; }
 private:
-    std::shared_ptr<Type> ptr_{};
+    std::shared_ptr<object_proxy<Type>> ptr_{};
     utils::identifier pk_;
 };
 

include/matador/orm/session.hpp

@@ -63,7 +63,7 @@ public:
     if (!obj->get()) {
       return utils::failure(make_error(error_code::FailedToFindObject, "Failed to find object of type " + info->get().name() + " with primary key " + std::to_string(pk) + "."));
     }
-    return utils::ok(object::object_ptr<Type>{ obj.release() });
+    return utils::ok(object::object_ptr<Type>{ obj->release() });
   }
 
   template<typename Type>

test/core/object/PrimaryKeyResolverTest.cpp

@@ -3,6 +3,7 @@
 #include "matador/object/primary_key_resolver.hpp"
 
 #include "../test/models/book.hpp"
+#include "../test/models/author.hpp"
 #include "../test/models/product.hpp"
 
 TEST_CASE("Test primary key resolver", "[PrimaryKeyResolver]") {