[Global]: loading init

deps/json/docs/examples/json_base_class_t.cpp

@@ -0,0 +1,88 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+class visitor_adaptor_with_metadata
+{
+  public:
+    template <class Fnc>
+    void visit(const Fnc& fnc) const;
+
+    int metadata = 42;
+  private:
+    template <class Ptr, class Fnc>
+    void do_visit(const Ptr& ptr, const Fnc& fnc) const;
+};
+
+using json = nlohmann::basic_json <
+             std::map,
+             std::vector,
+             std::string,
+             bool,
+             std::int64_t,
+             std::uint64_t,
+             double,
+             std::allocator,
+             nlohmann::adl_serializer,
+             std::vector<std::uint8_t>,
+             visitor_adaptor_with_metadata
+             >;
+
+template <class Fnc>
+void visitor_adaptor_with_metadata::visit(const Fnc& fnc) const
+{
+    do_visit(json::json_pointer{}, fnc);
+}
+
+template <class Ptr, class Fnc>
+void visitor_adaptor_with_metadata::do_visit(const Ptr& ptr, const Fnc& fnc) const
+{
+    using value_t = nlohmann::detail::value_t;
+    const json& j = *static_cast<const json*>(this);
+    switch (j.type())
+    {
+        case value_t::object:
+            fnc(ptr, j);
+            for (const auto& entry : j.items())
+            {
+                entry.value().do_visit(ptr / entry.key(), fnc);
+            }
+            break;
+        case value_t::array:
+            fnc(ptr, j);
+            for (std::size_t i = 0; i < j.size(); ++i)
+            {
+                j.at(i).do_visit(ptr / std::to_string(i), fnc);
+            }
+            break;
+        case value_t::null:
+        case value_t::string:
+        case value_t::boolean:
+        case value_t::number_integer:
+        case value_t::number_unsigned:
+        case value_t::number_float:
+        case value_t::binary:
+            fnc(ptr, j);
+            break;
+        case value_t::discarded:
+        default:
+            break;
+    }
+}
+
+int main()
+{
+    // create a json object
+    json j;
+    j["null"];
+    j["object"]["uint"] = 1U;
+    j["object"].metadata = 21;
+
+    // visit and output
+    j.visit(
+        [&](const json::json_pointer & p,
+            const json & j)
+    {
+        std::cout << (p.empty() ? std::string{"/"} : p.to_string())
+                  << " - metadata = " << j.metadata << " -> " << j.dump() << '\n';
+    });
+}