Question

我正在使用Qt5。我试图从json对象获取值。以下是json对象的样子，我试图从中获取数据：

{
    "success": true,
    "properties": [
        {
            "ID": 1001,
            "PropertyName": "McDonalds",
            "key": "00112233445566778899aabbccddeeff"
        },
        {
            "ID": 1002,
            "PropertyName": "Burger King",
            "key": "10112233445566778899aabbccddeeff"
        },
        {
            "ID": 1003,
            "PropertyName": "Taco Bell",
            "key": "20112233445566778899aabbccddeeff"
        }
    ]
}

如何在Qt中创建三个包含属性[x] .ID，属性[x] .PropertyName和属性[x] .key的数组？

编辑：

使用QScriptEngine我试过这个：

QString data = (QString)reply->readAll();

QScriptEngine engine;

QScriptValue result = engine.evaluate(data);

qDebug() << result.toString();

Debug说“SyntaxError：Parse error”

Answer 1

我明白了：

QStringList propertyNames;
QStringList propertyKeys;
QString strReply = (QString)reply->readAll();
QJsonDocument jsonResponse = QJsonDocument::fromJson(strReply.toUtf8());
QJsonObject jsonObject = jsonResponse.object();
QJsonArray jsonArray = jsonObject["properties"].toArray();

foreach (const QJsonValue & value, jsonArray) {
    QJsonObject obj = value.toObject();
    propertyNames.append(obj["PropertyName"].toString());
    propertyKeys.append(obj["key"].toString());
}

Answer 2

这是一个例子 How To Manipulate JSON With C++ and Qt

// reads a json file from disk to QVariantMap
// originally from http://erickveil.github.io/2016/04/06/How-To-Manipulate-JSON-With-C++-and-Qt.html
bool readJsonFile(std::string file_path, QVariantMap& result)
{
    // step 1
    QFile file_obj(QString::fromStdString(file_path));
    if (!file_obj.open(QIODevice::ReadOnly)) {
    std::cout << "Failed to open " << file_path << std::endl;
    exit(1);
    }

    // step 2
    QTextStream file_text(&file_obj);
    QString json_string;
    json_string = file_text.readAll();
    file_obj.close();
    QByteArray json_bytes = json_string.toLocal8Bit();

    // step 3
    auto json_doc = QJsonDocument::fromJson(json_bytes);

    if (json_doc.isNull()) {
        std::cout << "Failed to create JSON doc." << std::endl;
        return false;
    }
    if (!json_doc.isObject()) {
        std::cout << "JSON is not an object." << std::endl;
        return false;
    }

    QJsonObject json_obj = json_doc.object();

    if (json_obj.isEmpty()) {
        std::cout << "JSON object is empty." << std::endl;
        return false;
    }

    // step 4
    result = json_obj.toVariantMap();
    return true;
}

// writes a QVariantMap to disk
bool writeJsonFile(QVariantMap point_map, std::string file_path)
{
    QJsonObject json_obj = QJsonObject::fromVariantMap(point_map);
    QJsonDocument json_doc(json_obj);
    QString json_string = json_doc.toJson();

    QFile save_file(QString::fromStdString(file_path));
    if (!save_file.open(QIODevice::WriteOnly)) {
        std::cout << "failed to open save file" << std::endl;
        return false;
    }
    save_file.write(json_string.toLocal8Bit());
    save_file.close();
    return true;
}

Qt使用QJsonDocument，QJsonObject，QJsonArray解析JSON

2 个答案: