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{{KBCS}}
{{CodeSnippet
|id=CS001390
|platform=S60 3rd Edition, FP1, FP2<br>S60 5th Edition
|devices=Nokia 5800 XpressMusic
|category=Qt for Symbian
|subcategory=Base/System
|creationdate=June 16, 2009
|keywords=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 (<tt>exampleplugininterface.h</tt>). 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 <tt>QPluginLoader</tt>.

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 [http://wiki.forum.nokia.com/index.php/Qt_for_S60_-_Installation_packages Qt for S60 - Installation packages]
* Check this link for installation guide: [http://pepper.troll.no/s60prereleases/doc/install-s60.html 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 <tt>virtual sayHello()</tt> method and the <tt>virtual someSlot()</tt> slot.
<code cpp>
#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");
</code>

==See also==

* [[CS001391 - Implementing the Qt plug-in interface]]
* [[CS001425 - Loading and initialising a Qt plug-in dynamically]]

* For more information about, see [http://doc.qtsoftware.com/4.5/plugins-howto.html How to Create Qt Plugins].


==Postconditions==
The Qt plug-in interface is defined.


[[Category:Qt]][[Category:Qt for Symbian]][[Category:Code Examples]][[Category:Base/System]]