use perfect forwarding with the visitor also

cbeck88 · Jun 25, 2016 · fb51bcb · fb51bcb
1 parent 3ea455a
commit fb51bcb
Show file tree

Hide file tree

Showing 6 changed files with 25 additions and 10 deletions.
diff --git a/include/visit_struct/visit_struct.hpp b/include/visit_struct/visit_struct.hpp
@@ -89,10 +89,10 @@ VISIT_STRUCT_CONSTEXPR auto apply_visitor(V && v, S && s) ->
  */
 
 #define VISIT_STRUCT_MEMBER_HELPER(MEMBER_NAME)                                        \
-  visitor(#MEMBER_NAME, struct_instance.MEMBER_NAME);
+  std::forward<V>(visitor)(#MEMBER_NAME, struct_instance.MEMBER_NAME);
 
 #define VISIT_STRUCT_MEMBER_HELPER_MOVE(MEMBER_NAME)                                   \
-  visitor(#MEMBER_NAME, std::move(struct_instance.MEMBER_NAME));
+  std::forward<V>(visitor)(#MEMBER_NAME, std::move(struct_instance.MEMBER_NAME));
 
 
 // This macro specializes the trait, provides "apply" method which does the work.

diff --git a/include/visit_struct/visit_struct_boost_fusion.hpp b/include/visit_struct/visit_struct_boost_fusion.hpp
@@ -37,11 +37,11 @@ struct visitable<S,
     V visitor;
     T struct_instance;
 
-    explicit helper(V v, T t) : visitor(v), struct_instance(t) {}
+    explicit helper(V v, T t) : visitor(std::forward<V>(v)), struct_instance(t) {}
 
     template <typename Index>
     void operator()(Index) const {
-      visitor(boost::fusion::extension::struct_member_name<S, Index::value>::call(), boost::fusion::at<Index>(struct_instance));
+      std::forward<V>(visitor)(boost::fusion::extension::struct_member_name<S, Index::value>::call(), boost::fusion::at<Index>(struct_instance));
     }
   };
 
@@ -50,33 +50,33 @@ struct visitable<S,
     V visitor;
     T struct_instance;
 
-    explicit helper_rvalue_ref(V v, T t) : visitor(v), struct_instance(std::move(t)) {}
+    explicit helper_rvalue_ref(V v, T t) : visitor(std::forward<V>(v)), struct_instance(std::move(t)) {}
 
     template <typename Index>
     void operator()(Index) const {
-      visitor(boost::fusion::extension::struct_member_name<S, Index::value>::call(), std::move(boost::fusion::at<Index>(struct_instance)));
+      std::forward<V>(visitor)(boost::fusion::extension::struct_member_name<S, Index::value>::call(), std::move(boost::fusion::at<Index>(struct_instance)));
     }
   };
 
 public:
   template <typename V>
   static void apply(V && v, const S & s) {
     typedef boost::mpl::range_c<unsigned, 0, boost::fusion::result_of::size<S>::value > Indices; 
-    helper<V, const S &> h{v, s};
+    helper<decltype(std::forward<V>(v)), const S &> h{std::forward<V>(v), s};
     boost::fusion::for_each(Indices(), h);
   }
 
   template <typename V>
   static void apply(V && v, S & s) {
     typedef boost::mpl::range_c<unsigned, 0, boost::fusion::result_of::size<S>::value > Indices; 
-    helper<V, S &> h{v, s};
+    helper<decltype(std::forward<V>(v)), S &> h{std::forward<V>(v), s};
     boost::fusion::for_each(Indices(), h);
   }
 
   template <typename V>
   static void apply(V && v, S && s) {
     typedef boost::mpl::range_c<unsigned, 0, boost::fusion::result_of::size<S>::value > Indices;
-    helper_rvalue_ref<V, S &&> h{v, std::move(s)};
+    helper_rvalue_ref<decltype(std::forward<V>(v)), S &&> h{std::forward<V>(v), std::move(s)};
     boost::fusion::for_each(Indices(), h);
   }
 

diff --git a/include/visit_struct/visit_struct_intrusive.hpp b/include/visit_struct/visit_struct_intrusive.hpp
@@ -132,7 +132,7 @@ template <typename M>
 struct member_helper {
   template <typename V, typename S>
   VISIT_STRUCT_CONSTEXPR static void apply_visitor(V && visitor, S && structure_instance) {
-    visitor(M::member_name, M::apply(std::forward<S>(structure_instance)));
+    std::forward<V>(visitor)(M::member_name, M::apply(std::forward<S>(structure_instance)));
   }
 };
 

diff --git a/test_visit_struct.cpp b/test_visit_struct.cpp
@@ -82,6 +82,11 @@ struct test_visitor_three {
   void operator()(const char *, int &&) {
     result = 3;
   }
+
+  // Make it non-copyable and non-moveable, apply visitor should still work.
+  test_visitor_three() = default;
+  test_visitor_three(const test_visitor_three &) = delete;
+  test_visitor_three(test_visitor_three &&) = delete;
 };
 
 

diff --git a/test_visit_struct_boost_fusion.cpp b/test_visit_struct_boost_fusion.cpp
@@ -88,6 +88,11 @@ struct test_visitor_three {
   void operator()(const char *, int &&) {
     result = 3;
   }
+
+  // Make it non-copyable and non-moveable, apply visitor should still work.
+  test_visitor_three() = default;
+  test_visitor_three(const test_visitor_three &) = delete;
+  test_visitor_three(test_visitor_three &&) = delete;
 };
 
 

diff --git a/test_visit_struct_intrusive.cpp b/test_visit_struct_intrusive.cpp
@@ -44,6 +44,11 @@ struct test_visitor_three {
   void operator()(const char *, int &&) {
     result = 3;
   }
+
+  // Make it non-copyable and non-moveable, apply visitor should still work.
+  test_visitor_three() = default;
+  test_visitor_three(const test_visitor_three &) = delete;
+  test_visitor_three(test_visitor_three &&) = delete;
 };
 
 // debug_print