QtJsonHelper is a set of classes for reading and writing JSON (http://json.org/). It uses the JSON classes in Qt 5 (http://qt-project.org/doc/qt-5/json.html) but provides a higher-level interface.

Since version 5.0, Qt includes classes to read and write JSON. While these aren't difficult to use, they can require a lot of boilerplate code, especially if you're parsing JSON and you want to have proper error checks. For example, the following code extracts a single field from a JSON object:

QJsonParseError pe;
QJsonDocument doc = QJsonDocument::fromJson(json, &pe);
if (pe.error != QJsonParseError::NoError) {
    std::cout << "Error: " << qPrintable(pe.errorString()) << "\n";
    return;
}
if ( ! doc.isObject()) {
    std::cout << "Error: expected JSON object\n";
    return;
}
QJsonObject o = doc.object();
if ( ! o.contains("name")) {
    std::cout << "Error: missing element 'name'\n";
    return;
}
QJsonValue nameValue = o.value("name");
if ( ! nameValue.isString()) {
    std::cout << "Error: element 'name' should be a string.\n";
    return;
}
QString name = nameValue.toString();
std::cout << "name: " << qPrintable(name) << "\n";

Here's the corresponding code using QtJsonHelper:

try {
    JsonObject o(json);
    QString name = o.string("name");
    std::cout << "name: " << qPrintable(name) << "\n";
} catch (const JsonException& e) {
    std::cout << "Error parsing JSON: " << qPrintable(e.what()) << "\n";
}

The easiest way to use the classes is to simply copy the source and header files (except main.cpp) into your C++ source code directory. Alternatively, you can change qtjsonhelper.pro to build a static or dynamic library from Qt Creator or using qmake directly.

See main.cpp for an example of how to use the API.

The code is copyright (c) 2014 Brain Innovation B.V., Maastricht, The Netherlands. It is open source under the terms of the MIT license (see accompanying file LICENSE).