Towards #108.

Author: ColinH

include/tao/json/binding/element.hpp

@@ -82,6 +82,8 @@ namespace tao::json::binding
          using class_t = C;
          using value_t = T;
 
+         using internal_t = std::decay_t< decltype( P( std::declval< const C >() ) ) >;
+
          [[nodiscard]] static decltype( auto ) read( const C& v )
          {
             return P( v );
@@ -103,6 +105,8 @@ namespace tao::json::binding
          using class_t = A;
          using value_t = std::decay_t< R >;
 
+         using internal_t = value_t;
+
          [[nodiscard]] static decltype( auto ) read( const A& v ) noexcept
          {
             return CP( v );
@@ -139,6 +143,8 @@ namespace tao::json::binding
          using class_t = A;
          using value_t = std::decay_t< R >;
 
+         using internal_t = value_t;
+
          [[nodiscard]] static decltype( auto ) read( const A& v ) noexcept
          {
             return CP( v );

include/tao/json/binding/member.hpp

@@ -27,6 +27,20 @@ namespace tao::json::binding
       }
    };
 
+   template< member_kind R, typename K, auto CP, auto P >
+   struct member2
+      : element2< CP, P >,
+        internal::type_key< K, typename binding::element2< CP, P >::internal_t >
+   {
+      static constexpr member_kind kind = R;
+
+      template< template< typename... > class Traits, typename C >
+      [[nodiscard]] static bool is_nothing( const C& x )
+      {
+         return json::internal::is_nothing< Traits >( binding::element2< CP, P >::read( x ) );
+      }
+   };
+
 }  // namespace tao::json::binding
 
 #endif

src/test/json/CMakeLists.txt

@@ -4,6 +4,7 @@ set(testsources
   big_list_of_naughty_strings.cpp
   binding_array.cpp
   binding_factory.cpp
+  binding_function.cpp
   binding_object.cpp
   binding_versions.cpp
   cbor.cpp

src/test/json/binding_function.cpp

@@ -0,0 +1,55 @@
+// Copyright (c) 2018-2021 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#include "test.hpp"
+
+#include <tao/json.hpp>
+
+namespace tao::json
+{
+   struct type_f
+   {
+      int private_a;
+      int private_b;
+   };
+
+   [[nodiscard]] int get_a( const type_f& f ) noexcept
+   {
+      return f.private_a + 10;
+   }
+
+   [[nodiscard]] int& set_a( type_f& f ) noexcept
+   {
+      return f.private_a;
+   }
+
+   [[nodiscard]] int get_b( const type_f& f )
+   {
+      return f.private_b + 20;
+   }
+
+   // void set_b( type_f& f, int& b ) noexcept
+   // {
+   //    f.private_b = b;
+   // }
+
+   template<>
+   struct traits< type_f >
+      : binding::object< binding::member2< binding::member_kind::required, TAO_JSON_STRING_T( "a" ), &get_a, &set_a >,
+                         binding::member< binding::member_kind::required, TAO_JSON_STRING_T( "b" ), &get_b > >
+   {
+      TAO_JSON_DEFAULT_KEY( "f" );
+   };
+
+   void unit_test()
+   {
+      const type_f f{ 41, 42 };
+      const value v = produce::to_value( f );
+      TEST_ASSERT( v.get_object().size() == 2 );
+      TEST_ASSERT( v.get_object().at( "a" ).as< int >() == 51 );
+      TEST_ASSERT( v.get_object().at( "b" ).as< int >() == 62 );
+   }
+
+}  // namespace tao::json
+
+#include "../../test/json/main.hpp"