Add support in the SqlBinder class and the Session class (#644)

CMakeLists.txt

@@ -414,6 +414,7 @@ set(DROGON_UTIL_HEADERS
     lib/inc/drogon/utils/Utilities.h
     lib/inc/drogon/utils/any.h
     lib/inc/drogon/utils/string_view.h
+    lib/inc/drogon/utils/optional.h
     lib/inc/drogon/utils/HttpConstraint.h
     lib/inc/drogon/utils/OStringStream.h)
 install(FILES ${DROGON_UTIL_HEADERS}

examples/simple_example/TimeFilter.cc

@@ -16,16 +16,16 @@ void TimeFilter::doFilter(const HttpRequestPtr &req,
         cb(resp);
         return;
     }
-    if (req->session()->find(VDate))
+    auto lastDate = req->session()->getOptional<trantor::Date>(VDate);
+    if (lastDate)
     {
-        auto lastDate = req->session()->get<trantor::Date>(VDate);
-        LOG_TRACE << "last:" << lastDate.toFormattedString(false);
+        LOG_TRACE << "last:" << lastDate.value().toFormattedString(false);
         req->session()->modify<trantor::Date>(VDate,
                                               [now](trantor::Date &vdate) {
                                                   vdate = now;
                                               });
         LOG_TRACE << "update visitDate";
-        if (now > lastDate.after(10))
+        if (now > lastDate.value().after(10))
         {
             // 10 sec later can visit again;
             ccb();

lib/inc/drogon/Session.h

@@ -15,6 +15,7 @@
 #pragma once
 
 #include <drogon/utils/any.h>
+#include <drogon/utils/optional.h>
 #include <trantor/utils/Logger.h>
 #include <map>
 #include <memory>
@@ -59,6 +60,35 @@ class Session
         }
         return T();
     }
+
+    /**
+     * @brief Get the data identified by the key parameter and return an
+     * optional object that wraps the data.
+     *
+     * @tparam T
+     * @param key
+     * @return optional<T>
+     */
+    template <typename T>
+    optional<T> getOptional(const std::string &key) const
+    {
+        {
+            std::lock_guard<std::mutex> lck(mutex_);
+            auto it = sessionMap_.find(key);
+            if (it != sessionMap_.end())
+            {
+                if (typeid(T) == it->second.type())
+                {
+                    return optional<T>{*(any_cast<T>(&(it->second)))};
+                }
+                else
+                {
+                    LOG_ERROR << "Bad type";
+                }
+            }
+        }
+        return optional<T>{};
+    }
     /**
      * @brief Modify or visit the data identified by the key parameter.
      *

lib/inc/drogon/utils/optional.h

@@ -0,0 +1,29 @@
+/**
+ *
+ *  optional.h
+ *  An Tao
+ *
+ *  Copyright 2018, An Tao.  All rights reserved.
+ *  https://github.com/an-tao/drogon
+ *  Use of this source code is governed by a MIT license
+ *  that can be found in the License file.
+ *
+ *  Drogon
+ *
+ */
+
+#pragma once
+#if __cplusplus >= 201703L || (defined _MSC_VER && _MSC_VER > 1900)
+#include <optional>
+#else
+#include <boost/optional.hpp>
+#endif
+
+namespace drogon
+{
+#if __cplusplus >= 201703L || (defined _MSC_VER && _MSC_VER > 1900)
+using std::optional;
+#else
+using boost::optional;
+#endif
+}  // namespace drogon

orm_lib/inc/drogon/orm/SqlBinder.h

@@ -20,6 +20,7 @@
 #include <drogon/orm/Row.h>
 #include <drogon/orm/RowIterator.h>
 #include <drogon/utils/string_view.h>
+#include <drogon/utils/optional.h>
 #include <trantor/utils/Logger.h>
 #include <functional>
 #include <iostream>
@@ -436,7 +437,24 @@ class SqlBinder
         mode_ = mode;
         return *this;
     }
-
+    template <typename T>
+    self &operator<<(const optional<T> &parameter)
+    {
+        if (parameter)
+        {
+            return *this << parameter.value();
+        }
+        return *this << nullptr;
+    }
+    template <typename T>
+    self &operator<<(optional<T> &&parameter)
+    {
+        if (parameter)
+        {
+            return *this << std::move(parameter.value());
+        }
+        return *this << nullptr;
+    }
     void exec() noexcept(false);
 
   private: