new json loading helpers

json/json_functions.h

@@ -296,6 +296,44 @@ template <typename T> bool loadjson(const jsonval& parent, const std::string& ke
     return true;
 }
 
+template <typename T> bool loadjson(const jsonval& parent, const std::string& key, T& item, void (*f)(const std::string&, T&), const bool exist = true, bool* loaded = nullptr)
+{
+    try {
+        jsonval::ConstMemberIterator itr;
+        if (!extract_value(parent, key, exist, loaded, itr)) {
+            return false;
+        }
+
+        if(!itr->value.IsString()) {
+            throw Exp() << "element is not an string";
+        }
+
+        f(itr->value.GetString(), item);
+    }
+    catch (std::exception& e) {
+        throw Exp() << "failed to load key '" << key << "'" << " - " << trim(e.what()) << "\n";
+    }
+
+    return true;
+}
+
+template <typename T> bool loadjson(const std::map<std::string, std::string>& parent, const std::string& key, T& item, void (*f)(const std::string&, T&), const bool exist = true, bool* loaded = nullptr)
+{
+    try {
+        std::map<std::string, std::string>::const_iterator itr;
+        if (!extract_value(parent, key, exist, loaded, itr)) {
+            return false;
+        }
+
+        f(itr->second, item);
+    }
+    catch (std::exception& e) {
+        throw Exp() << "failed to load key '" << key << "'" << " - " << trim(e.what()) << "\n";
+    }
+
+    return true;
+}
+
 static bool loadjson(const std::map<std::string, std::string>& parent, const std::string& key, svalue<std::string>& value, const bool exist = true)
 {
     try {
@@ -749,9 +787,9 @@ template <typename T, typename TK> void PutValue(jsonalloc& alc, jsonval& ss, co
 template <typename T, typename TK> void PutMapAsVec(jsonalloc& alc, jsonval& ss, const std::string& conName, const std::map<TK, T>& vec, bool (*f)(rapidjson::Document::AllocatorType&, jsonval&, const T&))
 {
     jsonval jsvec(rapidjson::kArrayType);
-    for (auto& it = vec.begin(); it != vec.end(); ++it) {
+    for (const auto& it : vec) {
         jsonval child(rapidjson::kObjectType);
-        if (f(alc, child, it->second)) {
+        if (f(alc, child, it.second)) {
             jsvec.PushBack(child, alc);
         }
     }