用Qt序列化 [英] Serialization with Qt

问题描述

我正在使用Qt库编程GUI。在我的GUI我有一个巨大的std ::地图。

MyType是一个类有不同种类的字段。

我想序列化std :: map。我该怎么办？ QDataStream是否处理各种C ++和Qt数据类型？QDataStream是什么？Qt是什么？完整列表位于 http://qt-project.org/doc/qt-4.8/datastreamformat。 html 。我们还可以通过重载<<<和>>运算符。以下是可用于QDataStream的自定义数据类型的定义：

 类绘画
 {
 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）; 
  

以下是我们如何实现<操作符：

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

要输出绘画，我们只需输出两个QStrings和一个quint32。在函数的结尾，我们返回流。这是一个常见的C ++成语，它允许我们使用<<运算符与输出流。例如：

out<< painting1<< painting2<

操作符>>（）的实现类似于< pre> QDataStream& operator>>（QDataStream& in，Painting& painting）
{
QString title;
QString artist;
quint32 year;
在>> title>>艺术家>>年;
painting =绘画（标题，艺术家，年）;
return in;
}


这是从C ++ GUI编程与Qt 4由Jasmin Blanchette，Mark Summerfield

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

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

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

解决方案

QDataStream handles a variety of C++ and Qt data types. The complete list is available at http://qt-project.org/doc/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);

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;
}

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:

out << painting1 << painting2 << painting3;

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;
}

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

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