From 6a10575860cb5c966829f13db2d43a302d6bad70 Mon Sep 17 00:00:00 2001
From: Nomango <nomango@qq.com>
Date: Wed, 15 Apr 2020 16:37:28 +0800
Subject: [PATCH] use static_assert instead of template meta programming

---
 src/kiwano/core/EventDispatcher.h |  6 ++++--
 src/kiwano/core/EventListener.h   |  6 ++++--
 src/kiwano/core/event/Event.h     | 15 ++++++++-------
 3 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/src/kiwano/core/EventDispatcher.h b/src/kiwano/core/EventDispatcher.h
index 741ac100..2eff0bf2 100644
--- a/src/kiwano/core/EventDispatcher.h
+++ b/src/kiwano/core/EventDispatcher.h
@@ -51,9 +51,10 @@ public:
     /// @brief 添加监听器
     /// @tparam _EventTy 事件类型
     /// @param callback 回调函数
-    template <typename _EventTy, typename = typename std::enable_if<IsEvent<_EventTy>::value, int>::type>
+    template <typename _EventTy>
     EventListener* AddListener(EventListener::Callback callback)
     {
+        static_assert(kiwano::IsEvent<_EventTy>::value, "_EventTy is not an event type.");
         return AddListener(KGE_EVENT(_EventTy), callback);
     }
 
@@ -62,9 +63,10 @@ public:
     /// @tparam _EventTy 事件类型
     /// @param name 监听器名称
     /// @param callback 回调函数
-    template <typename _EventTy, typename = typename std::enable_if<IsEvent<_EventTy>::value, int>>
+    template <typename _EventTy>
     EventListener* AddListener(const String& name, EventListener::Callback callback)
     {
+        static_assert(kiwano::IsEvent<_EventTy>::value, "_EventTy is not an event type.");
         return AddListener(name, KGE_EVENT(_EventTy), callback);
     }
 
diff --git a/src/kiwano/core/EventListener.h b/src/kiwano/core/EventListener.h
index bdbcece7..2aee0e19 100644
--- a/src/kiwano/core/EventListener.h
+++ b/src/kiwano/core/EventListener.h
@@ -71,9 +71,10 @@ public:
     /// @brief 创建监听器
     /// @tparam _EventTy 事件类型
     /// @param callback 回调函数
-    template <typename _EventTy, typename = typename std::enable_if<IsEvent<_EventTy>::value, int>::type>
+    template <typename _EventTy>
     static inline EventListenerPtr Create(const Callback& callback)
     {
+        static_assert(kiwano::IsEvent<_EventTy>::value, "_EventTy is not an event type.");
         return EventListener::Create(KGE_EVENT(_EventTy), callback);
     }
 
@@ -82,9 +83,10 @@ public:
     /// @tparam _EventTy 事件类型
     /// @param name 监听器名称
     /// @param callback 回调函数
-    template <typename _EventTy, typename = typename std::enable_if<IsEvent<_EventTy>::value, int>::type>
+    template <typename _EventTy>
     static inline EventListenerPtr Create(const String& name, const Callback& callback)
     {
+        static_assert(kiwano::IsEvent<_EventTy>::value, "_EventTy is not an event type.");
         return EventListener::Create(name, KGE_EVENT(_EventTy), callback);
     }
 
diff --git a/src/kiwano/core/event/Event.h b/src/kiwano/core/event/Event.h
index 9288133e..09d182e4 100644
--- a/src/kiwano/core/event/Event.h
+++ b/src/kiwano/core/event/Event.h
@@ -55,19 +55,19 @@ public:
     /// \~chinese
     /// @brief 判断事件类型
     /// @return 是否是指定事件类型
-    template <typename _Ty, typename = typename std::enable_if<std::is_base_of<Event, _Ty>::value, int>::type>
+    template <typename _Ty>
     bool IsType() const;
 
     /// \~chinese
     /// @brief 安全转换为其他类型事件
     /// @throw std::bad_cast 类型无法转换时抛出
-    template <typename _Ty, typename = typename std::enable_if<std::is_base_of<Event, _Ty>::value, int>::type>
+    template <typename _Ty>
     const _Ty* SafeCast() const;
 
     /// \~chinese
     /// @brief 安全转换为其他类型事件
     /// @throw std::bad_cast 类型无法转换时抛出
-    template <typename _Ty, typename = typename std::enable_if<std::is_base_of<Event, _Ty>::value, int>::type>
+    template <typename _Ty>
     _Ty* SafeCast();
 
 private:
@@ -99,22 +99,23 @@ inline const EventType& Event::GetType() const
     return type_;
 }
 
-template <typename _Ty, typename>
+template <typename _Ty>
 inline bool Event::IsType() const
 {
+    static_assert(kiwano::IsEvent<_Ty>::value, "_Ty is not an event type.");
     return kiwano::IsEventType<_Ty>()(this);
 }
 
-template <typename _Ty, typename>
+template <typename _Ty>
 inline const _Ty* Event::SafeCast() const
 {
     return const_cast<Event*>(this)->SafeCast<_Ty>();
 }
 
-template <typename _Ty, typename>
+template <typename _Ty>
 inline _Ty* Event::SafeCast()
 {
-    if (!IsType<_Ty>())
+    if (!this->IsType<_Ty>())
         throw std::bad_cast();
     return dynamic_cast<_Ty*>(this);
 }