qt json

Simple introduction
json The basic rule ：

1. Data usage name / Value pairs indicate .
2. Use braces to save objects , Each name is followed by ‘:’（ The colon ）, name / Value for use ,（ comma ） Division .
3. Save the array with square brackets , Array values use ,（ comma ） Division .

class QJsonValue

For encapsulation JSON value

class QJsonObject

Responsible for packaging JSON object , It's a key / List of value pairs , Where key is the only string , Values are determined by QJsonValue Express .
Initialization mode ：

QJsonObject jsonObject;
jsonObject["key1"] = 1;
jsonObject["key2"] = 6.6;
jsonObject.insert("key3", "Hello world");
jsonObject["array"] = QJsonArray({
    1, 2, 3}); 
// perhaps 
QJsonObject jsonObject
{
    
    {
    "key1", 1},
    {
    "key2", 6.6},
    {
    "key3", "Hello world"},
    {
    "array", QJsonArray({
    1, 2, 3})}
};

QJsonArray

Responsible for packaging JSON Array ,JSON An array is a list of values , Interface and QVariantList similar ,QJsonArray And QVariantList Can be converted to each other .
QJsonList Operate on QList be similar , All have size()、insert() and removeAt() Wait for the operation , You can also use standard C++ The iterator pattern iterates over its contents .
Direct assignment uses ：

QJsonArray jsonArray = {
     1, 6.6, QString("Hello world") };

Interface operation use ：

QJsonArray jsonArray;
jsonArray.append(1);
jsonArray.append(6.6);
jsonArray.insert(2, "Hello world");

QJsonDocument

// Use QJsonDocument Set the json object
QJsonDocument jsonDoc;
jsonDoc.setObject(jsonObject);

// take json Write the file as text and close the file .
file.write(jsonDoc.toJson());
file.close();

practice

{
    
    "Company": "Digia",
    "From": 1991,
    "Name": "Qt",
    "Page": {
    
        "Developers": "https://www.qt.io/developers/",
        "Download": "https://www.qt.io/download/",
        "Home": "https://www.qt.io/"
    },
    "Version": [
        4.8,
        5.2,
        5.7
    ]
}

among "Page" The value of is a QJsonObject object ,"Version" It's a list

//  structure  Json  Array  - Version
QJsonArray versionArray;
versionArray.append(4.8);
versionArray.append(5.2);
versionArray.append(5.7);
 
//  structure  Json  object  - Page
QJsonObject pageObject;
pageObject.insert("Home", "https://www.qt.io/");
pageObject.insert("Download", "https://www.qt.io/download/");
pageObject.insert("Developers", "https://www.qt.io/developers/");
 
//  structure  Json  object 
QJsonObject json;
json.insert("Name", "Qt");
json.insert("Company", "Digia");
json.insert("From", 1991);
json.insert("Version", QJsonValue(versionArray));
json.insert("Page", QJsonValue(pageObject));
 
//  structure  Json  file 
QJsonDocument document;
document.setObject(json);
QByteArray byteArray = document.toJson(QJsonDocument::Compact);
QString strJson(byteArray);
 
qDebug() << strJson;
 

QString and QJsonObject The mutual transformation of

// QString >> QJson
QJsonObject getJsonObjectFromString(const QString jsonString){
    
    QJsonDocument jsonDocument = QJsonDocument::fromJson(jsonString.toLocal8Bit().data());
    if( jsonDocument.isNull() ){
    
        qDebug()<< "===> please check the string "<< jsonString.toLocal8Bit().data();
    }
    QJsonObject jsonObject = jsonDocument.object();
    return jsonObject;
}
// QJson >> QString
QString getStringFromJsonObject(const QJsonObject& jsonObject){
    
    return QString(QJsonDocument(jsonObject).toJson());
}