c++ - 在 Qt 中使用 QJsonDocument 解析嵌套的 JSON

Question

我有兴趣了解如何使用 Qt 的 QJsonDocument 来解析来自简单嵌套 JSON 的所有条目(因为我刚刚开始研究这个)。

嵌套的 json 示例:

{
    "city": "London",
    "time": "16:42",
    "unit_data": 
        [
            {
                "unit_data_id": "ABC123",
                "unit_data_number": "21"
            },
            {
                "unit_data_id": "DEF456",
                "unit_data_number": "12"
            }
        ]
}

我可以像这样解析它的非嵌套部分:

QJsonObject jObj;
QString city = jObj["city"].toString();
QString time = jObj["time"].toString();

Answer 1

我不确定你在问什么，但也许这可能会有所帮助:

QJsonDocument doc;
doc = QJsonDocument::fromJson("{                                              "
                              "     \"city\": \"London\",                      "
                              "     \"time\": \"16:42\",                       "
                              "     \"unit_data\":                             "
                              "         [                                      "
                              "             {                                  "
                              "                 \"unit_data_id\": \"ABC123\",  "
                              "                 \"unit_data_number\": \"21\"   "
                              "             },                                 "
                              "             {                                  "
                              "                 \"unit_data_id\": \"DEF456\",  "
                              "                 \"unit_data_number\": \"12\"   "
                              "             }                                  "
                              "         ]                                      "
                              " }");

// This part you have covered
QJsonObject jObj = doc.object();
qDebug() << "city" << jObj["city"].toString();
qDebug() << "time" << jObj["time"].toString();
// Since unit_data is an array, you need to get it as such
QJsonArray array = jObj["unit_data"].toArray();
// Then you can manually access the elements in the array
QJsonObject ar1 = array.at(0).toObject();
qDebug() << "" << ar1["unit_data_id"].toString();
// Or you can loop over the items in the array
int idx = 0;
for(const QJsonValue& val: array) {
    QJsonObject loopObj = val.toObject();
    qDebug() << "[" << idx << "] unit_data_id    : " << loopObj["unit_data_id"].toString();
    qDebug() << "[" << idx << "] unit_data_number: " << loopObj["unit_data_number"].toString();
    ++idx;
}

我得到的输出是:

city "London"
time "16:42"
"ABC123"
[ 0 ] unit_data_id    :  "ABC123"
[ 0 ] unit_data_number:  "21"
[ 1 ] unit_data_id    :  "DEF456"
[ 1 ] unit_data_number:  "12"