类中是基本数据类型，自动实现深拷贝

#include <QCoreApplication>
#include <QDebug>
class C {
public:
    QByteArray ba;
    QString str;
    qint32 num;
};
int main()
{
    const char buf[] = "hello";
    C c1;
    c1.ba = QByteArray(buf);
    c1.num = 100;
    C c2(c1); // 调用拷贝构造函数
    C c3 = c1; // 调用赋值运算符
    qDebug() << c2.ba << ", " << c2.num;
    qDebug() << c3.ba << ", " << c3.num;
    return 0;
}
// 输出结果
// "hello" ,  100
// "hello" ,  100