2 files changed, 82 insertions, 15 deletions

diff --git a/include/cru/common/Event2.h b/include/cru/common/Event2.h
index 5677828a..62fb366d 100644
--- a/include/cru/common/Event2.h
+++ b/include/cru/common/Event2.h
@@ -10,6 +10,13 @@
 #include <vector>
 
 namespace cru {
+class Event2Base {
+ public:
+  virtual ~Event2Base() = default;
+
+  virtual void RevokeHandler(int token_value) = 0;
+};
+
 template <typename TArgument, typename TResult>
 class EventContext {
  public:
@@ -46,20 +53,19 @@ constexpr bool is_event2_v = false;
 template <typename TArgument, typename TResult>
 constexpr bool is_event2_v<Event2<TArgument, TResult>> = true;
 
-template <typename TEvent2>
 class EventHandlerToken {
-  static_assert(is_event2_v<TEvent2>, "TEvent2 must be Event2 class.");
-
  public:
-  EventHandlerToken(ObjectResolver<TEvent2> event_resolver, int token_value)
+  EventHandlerToken(ObjectResolver<Event2Base> event_resolver, int token_value)
       : event_resolver_(std::move(event_resolver)), token_value_(token_value) {}
 
-  ObjectResolver<TEvent2> GetEventResolver() const { return event_resolver_; }
+  ObjectResolver<Event2Base> GetEventResolver() const {
+    return event_resolver_;
+  }
   int GetTokenValue() const { return token_value_; }
-  void RevokeHandler() const;
+  inline void RevokeHandler() const;
 
  private:
-  ObjectResolver<TEvent2> event_resolver_;
+  ObjectResolver<Event2Base> event_resolver_;
   int token_value_;
 };
 
@@ -79,9 +85,10 @@ struct Event2BehaviorFlags {
 
 template <typename TArgument = std::nullptr_t,
           typename TResult = std::nullptr_t>
-class Event2 : public SelfResolvable<Event2<TArgument, TResult>> {
+class Event2 : public Event2Base,
+               public SelfResolvable<Event2<TArgument, TResult>> {
  public:
-  using HandlerToken = EventHandlerToken<Event2>;
+  using HandlerToken = EventHandlerToken;
   using Context = EventContext<TArgument, TResult>;
   using Handler = std::function<void(Context*)>;
   using SpyOnlyHandler = std::function<void()>;
@@ -122,7 +129,7 @@ class Event2 : public SelfResolvable<Event2<TArgument, TResult>> {
     return HandlerToken(this->CreateResolver(), token);
   }
 
-  void RevokeHandler(int token_value) {
+  void RevokeHandler(int token_value) override {
     auto iter = this->handlers_.cbegin();
     auto end = this->handlers_.cend();
     for (; iter != end; ++iter) {
@@ -184,8 +191,7 @@ class Event2 : public SelfResolvable<Event2<TArgument, TResult>> {
   Event2BehaviorFlag flags_;
 };
 
-template <typename TEvent2>
-void EventHandlerToken<TEvent2>::RevokeHandler() const {
+inline void EventHandlerToken::RevokeHandler() const {
   auto event = this->event_resolver_.Resolve();
   if (event) {
     event->RevokeHandler(this->token_value_);
diff --git a/include/cru/common/SelfResolvable.h b/include/cru/common/SelfResolvable.h
index ce5b1628..84fa54f6 100644
--- a/include/cru/common/SelfResolvable.h
+++ b/include/cru/common/SelfResolvable.h
@@ -1,7 +1,9 @@
 #pragma once
 
 #include <cassert>
+#include <functional>
 #include <memory>
+#include <type_traits>
 
 namespace cru {
 template <typename T>
@@ -10,22 +12,74 @@ class SelfResolvable;
 template <typename T>
 class ObjectResolver {
   friend SelfResolvable<T>;
+  template <typename U>
+  friend class ObjectResolver;
 
  private:
-  explicit ObjectResolver(T* o) : shared_object_ptr_(new T*(o)) {}
+  template <typename U>
+  using Accessor_ = std::function<U*(const std::shared_ptr<void*>&)>;
+  using ThisAccessor_ = Accessor_<T>;
+
+  explicit ObjectResolver(T* o)
+      : shared_object_ptr_(new void*(o)),
+        accessor_([](const std::shared_ptr<void*>& ptr) {
+          return static_cast<T*>(*ptr);
+        }) {}
+  explicit ObjectResolver(std::shared_ptr<void*> ptr, ThisAccessor_ accessor)
+      : shared_object_ptr_(std::move(ptr)), accessor_(std::move(accessor)) {}
+
+  template <typename U>
+  static ThisAccessor_ CreateAccessor(Accessor_<U> parent_accessor) {
+    return [parent_accessor =
+                std::move(parent_accessor)](const std::shared_ptr<void*>& ptr) {
+      return static_cast<T*>(parent_accessor(ptr));
+    };
+  }
 
  public:
+  template <typename U,
+            typename = std::enable_if_t<std::is_convertible_v<U*, T*>>>
+  ObjectResolver(const ObjectResolver<U>& other)
+      : shared_object_ptr_(other.shared_object_ptr_),
+        accessor_(CreateAccessor(other.accessor_)) {}
+
+  template <typename U,
+            typename = std::enable_if_t<std::is_convertible_v<U*, T*>>>
+  ObjectResolver(ObjectResolver<U>&& other)
+      : shared_object_ptr_(std::move(other.shared_object_ptr_)),
+        accessor_(CreateAccessor(std::move(other.accessor_))) {}
+
   ObjectResolver(const ObjectResolver&) = default;
   ObjectResolver& operator=(const ObjectResolver&) = default;
   ObjectResolver(ObjectResolver&&) = default;
   ObjectResolver& operator=(ObjectResolver&&) = default;
   ~ObjectResolver() = default;
 
+  template <typename U,
+            typename = std::enable_if_t<std::is_convertible_v<U*, T*>>>
+  ObjectResolver& operator=(const ObjectResolver<U>& other) {
+    if (this != &other) {
+      this->shared_object_ptr_ = other.shared_object_ptr_;
+      this->accessor_ = CreateAccessor(other.accessor_);
+    }
+    return *this;
+  }
+
+  template <typename U,
+            typename = std::enable_if_t<std::is_convertible_v<U*, T*>>>
+  ObjectResolver& operator=(ObjectResolver<U>&& other) {
+    if (this != &other) {
+      this->shared_object_ptr_ = std::move(other.shared_object_ptr_);
+      this->accessor_ = CreateAccessor(std::move(other.shared_object_ptr_));
+    }
+    return *this;
+  }
+
   bool IsValid() const { return this->shared_object_ptr_ != nullptr; }
 
   T* Resolve() const {
     assert(IsValid());
-    return *this->shared_object_ptr_;
+    return this->accessor_(this->shared_object_ptr_);
   }
 
   /**
@@ -33,6 +87,12 @@ class ObjectResolver {
    */
   T* operator()() const { return Resolve(); }
 
+  template <typename U,
+            typename = std::enable_if_t<std::is_convertible_v<T*, U*>>>
+  operator ObjectResolver<U>() const {
+    return ObjectResolver<U>(*this);
+  }
+
  private:
   void SetResolvedObject(T* o) {
     assert(IsValid());
@@ -40,7 +100,8 @@ class ObjectResolver {
   }
 
  private:
-  std::shared_ptr<T*> shared_object_ptr_;
+  std::shared_ptr<void*> shared_object_ptr_;
+  std::function<T*(const std::shared_ptr<void*>&)> accessor_;
 };
 
 /**