From Forum Nokia Wiki

ID	CS001390	Creation date	June 16, 2009
Platform	S60 3rd Edition, FP1, FP2 S60 5th Edition	Tested on devices	Nokia 5800 XpressMusic
Category	Qt for Symbian	Subcategory	Base/System

Keywords (APIs, classes, methods, functions): QPluginLoader, Q_DECLARE_INTERFACE, Q_INTERFACES, Q_EXPORT_PLUGIN2

Overview

Qt applications can be extended with Qt plug-ins, which means that some of the application functionality is implemented as common plug-in libraries loaded into the application memory at runtime. To be extendable, the application has to define a common plug-in interface (exampleplugininterface.h). Note that the application does not see the plug-ins directly but only methods and data that are defined into the interface. The detection and loading of plug-ins is handled using QPluginLoader.

This code snippet demonstrates how to define the lower-level Qt plug-in interface. Implementing the interface and using the plug-in are described in additional snippet articles.

Note: In order to use this code, you need to have Qt for S60 installed on your platform.

Preconditions

• Install latest Qt for S60 see Qt for S60 - Installation packages
• Check this link for installation guide: How to install the package.
• Go through this article: Getting started with Qt for S60

Header (exampleplugininterface.h)

The plug-in interface for all "example plug-ins". The plug-in must implement the virtual sayHello() method and the virtual someSlot() slot.

#include <QObject>
#include <QString>
 
class ExamplePluginInterface : public QObject
    {
    public:
        virtual ~ExamplePluginInterface() {}
        virtual QString sayHello() = 0;
 
    public slots:        
        virtual void someSlot(QString value) = 0;
 
    protected: // Common data for the plugins
        QString data;
    };
 
// This Qt macro associates the given Identifier
// "Forum.Nokia.wiki.pluginsnippet.ExamplePluginInterface/1.0"
// to the interface class called ExamplePluginInterface. 
// The Identifier must be unique.
Q_DECLARE_INTERFACE(ExamplePluginInterface,
    "Forum.Nokia.wiki.pluginsnippet.ExamplePluginInterface/1.0");

See also

• CS001391 - Implementing the Qt plug-in interface
• CS001425 - Loading and initialising a Qt plug-in dynamically

• For more information about, see How to Create Qt Plugins.

Postconditions

The Qt plug-in interface is defined.