iterate and retrieve nested object in JSON using rapidjson

First, let me provide credit to MiloYip at this link

Second-- here's what I did for my project:

rapidjson::Document document;// document holds a json document retrieved from a http GET request// I did not include all of that in this example.  I am only showing// the part of iterating through a nested object and retrieving members.std::vector<std::string> symbols;// holds the values I retrieve from the json documentif (document.Parse<0>( symbol.c_str() ).HasParseError() )    Log() << "ERROR: encountered a JSON parsing error" << std::endl;else {    // Get the nested object that contains the elements I want.    // In my case, the nested object in my json document was results    // and the values I was after were identified as "t"    rapidjson::Value& results = document["results"];    assert(results.IsArray());    for (rapidjson::SizeType i = 0; i < results.Size(); i++) {        // Store the value of the element in a vector.        symbols.emplace_back(results[i]["t"].GetString());}                            

I think this is a pretty clean/efficient approach.

This is something I recently worked on:

void enter(const Value &obj, size_t indent = 0) { //print JSON treeif (obj.IsObject()) { //check if object    for (Value::ConstMemberIterator itr = obj.MemberBegin(); itr != obj.MemberEnd(); ++itr) {   //iterate through object           const Value& objName = obj[itr->name.GetString()]; //make object value        for (size_t i = 0; i != indent; ++i) //indent            cout << " ";        cout << itr->name.GetString() << ": "; //key name        if (itr->value.IsNumber()) //if integer            std::cout << itr->value.GetInt() ;        else if (itr->value.IsString()) //if string            std::cout << itr->value.GetString();        else if (itr->value.IsBool()) //if bool            std::cout << itr->value.GetBool();        else if (itr->value.IsArray()){ //if array            for (SizeType i = 0; i < itr->value.Size(); i++) {                if (itr->value[i].IsNumber()) //if array value integer                    std::cout << itr->value[i].GetInt() ;                else if (itr->value[i].IsString()) //if array value string                    std::cout << itr->value[i].GetString() ;                else if (itr->value[i].IsBool()) //if array value bool                    std::cout << itr->value[i].GetBool() ;                else if (itr->value[i].IsObject()){ //if array value object                    cout << "\n  ";                    const Value& m = itr->value[i];                     for (auto& v : m.GetObject()) { //iterate through array object                        if (m[v.name.GetString()].IsString()) //if array object value is string                            cout << v.name.GetString() << ": " <<   m[v.name.GetString()].GetString();                        else //if array object value is integer                            cout << v.name.GetString() << ": "  <<  m[v.name.GetString()].GetInt();                       cout <<  "\t"; //indent                    }                }                cout <<  "\t"; //indent            }        }        cout << endl;         enter(objName, indent + 1); //if couldn't find in object, enter object and repeat process recursively         }      } }

This can handle any type of JSON tree. All you have to do is pass a Value as such:

Value v = document.GetObject();Value& m= v;enter(m);

And you're done!

void parseRecursive(std::string scope                    , rapidjson::Value::ConstMemberIterator object                    , std::unordered_map<std::string, std::string>& values){    if (scope.empty())    {        scope = object->name.GetString();    }    else    {        scope = scope + "::" + object->name.GetString();    }    auto inElement = scope + "::";    if (object->value.IsObject())    {        for (auto it = object->value.MemberBegin(); it != object->value.MemberEnd(); ++it)        {            parseRecursive(scope, it, values);        }    }    else if (object->value.IsDouble())    {        values.emplace(inElement, std::to_string(object->value.GetDouble()));    }    else if (object->value.IsInt())    {        values.emplace(inElement, std::to_string(object->value.GetInt()));    }    else    {        LOGW("Unsuported: " << inElement << object->name.GetString());    }}

And start with document: rapidjson::Document document;

for (auto it = document.MemberBegin(); it != document.MemberEnd(); ++it){    parseRecursive("", it, _values);}