問題描述

我正在使用 Qt 庫編寫 GUI.在我的 GUI 中，我有一個巨大的 std::map.

I am programming a GUI with Qt library. In my GUI I have a huge std::map.

MyType"是一個具有不同類型字段的類.

"MyType" is a class that has different kinds of fields.

我想序列化 std::map.我怎樣才能做到這一點?Qt 是否為我們提供了必要的功能?

I want to serialize the std::map. How can I do that? Does Qt provides us with neccesary features?

推薦答案

QDataStream 處理各種 C++ 和 Qt 數據類型.完整列表可在 http://doc.qt.io/qt-4.8/datastreamformat.html.我們還可以通過重載 << 來添加對我們自己的自定義類型的支持.和 >> 運算符.以下是可與 QDataStream 一起使用的自定義數據類型的定義:

QDataStream handles a variety of C++ and Qt data types. The complete list is available at http://doc.qt.io/qt-4.8/datastreamformat.html. We can also add support for our own custom types by overloading the << and >> operators. Here's the definition of a custom data type that can be used with QDataStream:

class Painting
{
public:
    Painting() { myYear = 0; }
    Painting(const QString &title, const QString &artist, int year) {
        myTitle = title;
        myArtist = artist;
        myYear = year;
    }
    void setTitle(const QString &title) { myTitle = title; }
    QString title() const { return myTitle; }
    ...
private:
    QString myTitle;
    QString myArtist;
    int myYear;
};
QDataStream &operator<<(QDataStream &out, const Painting &painting);
QDataStream &operator>>(QDataStream &in, Painting &painting);

以下是我們如何實現 <<操作員:

Here's how we would implement the << operator:

QDataStream &operator<<(QDataStream &out, const Painting &painting)
{
    out << painting.title() << painting.artist()
        << quint32(painting.year());
    return out;
}

要輸出一幅畫，我們只需輸出兩個 QString 和一個 quint32.在函數結束時，我們返回流.這是一個常見的 C++ 習慣用法，它允許我們使用 <<具有輸出流的運算符.例如:

To output a Painting, we simply output two QStrings and a quint32. At the end of the function, we return the stream. This is a common C++ idiom that allows us to use a chain of << operators with an output stream. For example:

出<<繪畫1<<繪畫2<<繪畫3;

out << painting1 << painting2 << painting3;

operator>>()的實現與operator<<()類似:

The implementation of operator>>() is similar to that of operator<<():

QDataStream &operator>>(QDataStream &in, Painting &painting)
{
    QString title;
    QString artist;
    quint32 year;
    in >> title >> artist >> year;
    painting = Painting(title, artist, year);
    return in;
}

本文來自:C++ GUI Programming with Qt 4 By Jasmin Blanchette, Mark Summerfield

This is from: C++ GUI Programming with Qt 4 By Jasmin Blanchette, Mark Summerfield

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