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JSON解析实例（Qt含源码）

 2 years ago
source link: https://blog.51cto.com/u_15696298/5450150
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JSON解析

Qt中内置了一个QJsonDocument类用来处理json文件，以及json字符串。解析思路先将string加载到QJsonDocument中，然后将其逐层解析。json的格式包含两种，1）对象，2）数组

名字 解析
QJsonDocument 一个封装完整JSON文档的类，可以从UTF-8编码的基于文本的表示以及Qt自己的二进制格式读取和写入该文档
QJsonObject 是键值对的列表，其中键是唯一的字符串，值由QJsonValue表示。
QJsonArray JSON数组是一个值列表。可以通过从数组中插入和删除QJsonValue来操作该列表。
QJsonValue JSON是一种存储结构化数据的格式。它有6种基本数据类型：bool、double、string、array、object、null
QJsonParseError 用于在JSON解析期间报告错误 
{"Name":"小明","age":18}

Qt json解析对象 代码

void MainWindow::parseObject()
{
    QString str = "{\"Name\":\"小明\",\"Age\":18}";
    QJsonDocument jdoc = QJsonDocument::fromJson(str.toUtf8());
    QJsonObject jobject = jdoc.object();
    QJsonValue jvalue_name = jobject.value("Name");
    qInfo() << jvalue_name.toString();
    QJsonValue jvalue_age = jobject.value("Age");
    qInfo() << jvalue_age.toInt();

    ///////// 遍历 /////////////
    foreach (auto item, jobject.keys()) {
        qInfo() << "key:" << item;
        QJsonValue jvalue = jobject.value(item);
        qInfo() << "value:" << jvalue.toVariant();
    }
}

"小明"
18
key: "Age"
value: QVariant(double, 18)
key: "Name"
value: QVariant(QString, "小明")

["apple","orange","banana","watermelon"]

Qt json解析数组代码

void MainWindow::parseArray()
{
    QString str = "[\"apple\",\"orange\",\"banana\",\"watermelon\"]";
    QJsonDocument jdoc = QJsonDocument::fromJson(str.toUtf8());
    QJsonArray jArray = jdoc.array();
    // item 为QJsonValue类型
    foreach (auto item, jArray) {
        qInfo() << item.toString();
    }
}

"apple"
"orange"
"banana"
"watermelon"

数组对象混合解析

{"Lists":["apple","orange"]}

Qt json解析代码

void MainWindow::parseObjectArray()
{
    QString str = "{\"Lists\":[\"apple\",\"orange\"]}";
    QJsonDocument jdoc = QJsonDocument::fromJson(str.toUtf8());
    QJsonObject jObject = jdoc.object();
    QJsonValue jLists = jObject.value("Lists");
    QJsonArray jArray = jLists.toArray();
    // item 为QJsonValue类型
    foreach (auto item, jArray) {
        qInfo() << "value:" << item.toString();
    }
}

value: "apple"
value: "orange"

对象数组混合解析

[{"Name":"小明","age":18},{"Name":"小王","age":20}]

Qt 解析json代码

void MainWindow::parseArrayObject()
{
    QString str =
        "[{\"Name\":\"小明\",\"age\":18},{\"Name\":\"小王\",\"age\":20}]";
    QJsonDocument jdoc = QJsonDocument::fromJson(str.toUtf8());
    QJsonArray jLists = jdoc.array();
    foreach (auto item, jLists) {
        QJsonObject item_object = item.toObject();
        qInfo() << "===============================";
        qInfo() << "name:" << item_object.value("Name").toString();
        qInfo() << "age:" << item_object.value("age").toDouble();
    }
}

===============================
name: "小明"
age: 18
===============================
name: "小王"
age: 20

公众号：【qt小王子】

JSON解析实例（Qt含源码）_数组

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