QtMapStream - serialization of object class to QVariantMap.

benlau

Hi,

If you need to convert a lots of you own non-QObject based class to XML/YAML/JSON etc. You may be interested with my tiny project / class - QtMapStream.

Source code:
[url]https://gitorious.org/qtmapstream/qtmapstream#more[/url]

QVariantMap is a synonym of QMap<QString, QVariant>. It could represent any complex objects. Convert
a QVariantMap instance to data serialization formats like XML , JSON and YAML is much easier than
a complex objects in C++. However, convert a C++ class to QVariantMap is not strict forward. User
have to implements their own convertion function.

The QtMapStream provides an interface and utility to convert user's own C++ class , which is not based
on QObject , to QVariantMap and vice versa.

Example class:

[CODE] class Book {
public:
QString title;
int pages;
qreal rating;
}[/CODE]

You should add the QT_MAP_STREAMABLE / QT_MAP_STREAMABLE_ITEM macro to the class declaration:

[CODE] class Book {
public:
QString title;
int pages;
qreal rating;

QT_MAP_STREAMABLE(
    QT_MAP_STREAMABLE_ITEM(QString,title)
    QT_MAP_STREAMABLE_ITEM(int,pages)
    QT_MAP_STREAMABLE_ITEM(qreal,rating)
)

};[/CODE]

The macro will add <<,>> operators overloading with taking a QtMapStream to the class.

Convert to QVariantMap

[CODE]
Book book;
book.title = "Qt Developer Guides";
book.pages = 180;
book.rating = 10.0;

QtMapStream stream;
book >> stream;

QVariantMap source = stream.source(); // It will return the QVariantMap writen by the book instance.

qDebug() << source; // QMap(("pages", QVariant(int, 180) ) ( "rating" , QVariant(double, 10) ) ( "title" , QVariant(QString, "Qt Developer Guides") ) )
[/CODE]

Convert from QVariantMap

@
Book book;
QVariantMap map;
map["title"] = "Qt Developer Guides";
map["pages"] = 180;
map["rating"] = 10.0;

QtMapStream stream(map);
book << stream; // The book instance will be filled with the information in QVariantmap

QVariantMap remaining = stream.source(); // After run the << stream operators, written field will be removed from the source. Call source() should return an empty map.
@

QtMapStream also support QList type. However, QList type can not be converted to QVariant directly. You should declare the QList type with Q_DECLARE_METATYPE first.

Example:

@Q_DECLARE_METATYPE(QList<QString>)

class BookV2 {
public:
QString title;
int pages;
qreal rating;
QList<QString> authors;

QT_MAP_STREAMABLE(
    QT_MAP_STREAMABLE_ITEM(QString,title)
    QT_MAP_STREAMABLE_ITEM(int,pages)
    QT_MAP_STREAMABLE_ITEM(qreal,rating)
    QT_MAP_STREAMABLE_ITEM(QList<QString> ,authors)
)

};
@
Author : Ben Lau
License: New BSD