Qt笔记-Qt中Json存二进制文件并读取文件（QJsonObject、QJsonArray、QJsonDocument的使用）

深藏阁楼爱情的钟 2022-12-23 11:11 185阅读 0赞

程序运行截图如下：

![20201124181931340.png][]

文件如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxNzg0NDI3NjE_size_16_color_FFFFFF_t_70][]

源码如下：

#include <QCoreApplication>
    #include <QJsonDocument>
    #include <QJsonArray>
    #include <QJsonObject>
    #include <QFile>
    #include <QDebug>
    #include <QVector>
    
    class Student{
    public:
        int id;
        QString name;
        void write(QJsonObject &json) const{
    
            json["id"] = id;
            json["name"] = name;
        }
    
        void read(const QJsonObject &json){
    
            if (json.contains("id") && json["id"].isDouble())
                id = json["id"].toInt();
    
            if (json.contains("name") && json["name"].isString())
                name = json["name"].toString();
        }
    
        friend QDebug operator << (QDebug os, Student stu){
    
                os << "(" << stu.id << ", "
                   << stu.name << ")";
    
                return os;
            }
    
    };
    
    class MyClass{
    public:
        int id;
        QVector<Student> students;
    
        void read(const QJsonObject &json){
    
            if(json.contains("id") && json["id"].isDouble())
                id = json["id"].toInt();
    
            if(json.contains("students") && json["students"].isArray()){
    
                QJsonArray array = json["students"].toArray();
                for(int i = 0; i < array.size(); i++){
    
                    QJsonObject obj = array[i].toObject();
                    Student student;
                    student.read(obj);
                    this->students.append(student);
                }
            }
    
        }
    
        void write(QJsonObject &json) const{
    
            json["id"] = id;
            QJsonArray array;
            for(int i = 0; i < students.size(); i++){
    
                QJsonObject student;
                students.at(i).write(student);
                array.append(student);
            }
            json["students"] = array;
        }
    
        friend QDebug operator << (QDebug os, MyClass myClass){
    
                os << "(" << endl << myClass.id << ", ";
                for(int i = 0; i < myClass.students.size(); i++){
    
                    os << myClass.students.at(i);
                }
                os << endl << ")";
    
                return os;
            }
    };
    
    
    int main(int argc, char *argv[])
    {
        QCoreApplication a(argc, argv);
    
        Student s0;
        s0.id = 1000;
        s0.name = "朱小明";
    
        Student s1;
        s1.id = 1001;
        s1.name = "闰土";
    
        Student s2;
        s2.id = 1000;
        s2.name = "锅盖";
    
        Student s3;
        s3.id = 1003;
        s3.name = "王炸";
    
        MyClass myClass;
        myClass.id = 142203;
        myClass.students.append(s0);
        myClass.students.append(s1);
        myClass.students.append(s2);
        myClass.students.append(s3);
    
        QJsonObject json;
        myClass.write(json);
    
        QJsonDocument saveJson(json);
    
        QFile saveJsonFile("save.json");
        QFile saveBinaryFile("save.dat");
        if(!saveJsonFile.open(QIODevice::ReadWrite)){
    
            qDebug() << "open failed";
            return 0;
        }
    
        if(!saveBinaryFile.open(QIODevice::ReadWrite)){
    
            qDebug() << "open failed";
            return 0;
        }
    
        saveJsonFile.write(saveJson.toJson());
        saveJsonFile.close();
    
        saveBinaryFile.write(saveJson.toBinaryData());
        saveBinaryFile.close();
    
        qDebug() << "write over";
    
        QFile loadFile("save.dat");
        if(!loadFile.open(QIODevice::ReadOnly)){
    
            qDebug() << "open failed";
        }
    
        QByteArray data = loadFile.readAll();
        QJsonDocument loadDoc(QJsonDocument::fromBinaryData(data));
        MyClass readClass;
        readClass.read(loadDoc.object());
        loadFile.close();
    
        qDebug() << "read over";
        qDebug() << readClass;
    
        return a.exec();
    }

[20201124181931340.png]: /images/20221120/1b46e80701704950862e21d0c25d14bd.png
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