c++ - 保存并加载 QList 到文件

Question

我有一个 ContactData 类和一个包含 QList 的 FriendList 类，我重载了 <> 运算符。

---

contactdata.h

class ContactData
{
//all public for testing
public:
    ContactData();
    QString m_name;
    QString m_description;
    bool m_online; 
};

QDataStream &operator<<(QDataStream& out, ContactData& contactData);
QDataStream &operator>>(QDataStream& in, ContactData* contactData);

contactdata.cpp

QDataStream &operator<<(QDataStream &out, ContactData& contactData)
{
    out << contactData.m_name;
    out << contactData.m_description;
    return out;
}

QDataStream &operator>>(QDataStream &in, ContactData* contactData)
{
    in >> contactData->m_name;
    in >> contactData->m_description;
    return in;
}

---

friendlist.h

#include "contactdata.h"
typedef QList<ContactData*> TFriendList;

class FriendList
{
...
public:
TFriendList* m_list;
...
};

QDataStream &operator<<(QDataStream& out, FriendList& list);
QDataStream &operator>>(QDataStream& in, FriendList* list);

friendlist.cpp

QDataStream &operator<<(QDataStream& out, FriendList& list)
{
    for(int i = 0; i < list.size(); i++)
    {
        ContactData contact = *list.at(i);
        out << contact;
    }

    return out;
}

QDataStream &operator>>(QDataStream& in, FriendList* list)
{
    for(int i = 0; i < list->size(); i++)
    {
        ContactData* contact = list->m_list->at(i);
        in >> contact;
    }

    return in;
}

---

// typedef QList<ContactData*> TFriendList;
private:
    FriendList* m_friendList;

保存功能

QString path = "/friendlist.bin";
QFile file(path);

if (file.open(QIODevice::WriteOnly))
{
    QDataStream out(&file);
    out << m_friendList;
    file.close();
}

加载函数

QString path = "/friendlist.bin";
QFile file(path);
if(file.exists())
{
  if (file.open(QIODevice::ReadOnly))
  {
     QDataStream in(&file);
     in >> m_friendList;
     file.close();
     qDebug() << "FriendList.size() = " << m_friendList->size();
     }
}

---

它确实在所需的方向上保存了一个文件，但不幸的是加载给我一个大小为 0 的空列表。这就是我被困的地方..

有人能帮忙吗？

Answer 1

你不需要重载 >>和 << QList 的运算符, 当左侧运算符为 QDataStream 时它们已经存在

参见 the documentation

只要单个对象可以正确序列化和反序列化，所有 Qt 容器也应该序列化和反序列化。