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KDECore

KServiceTypeTrader Class Reference

KDE's trader interface (similar to the CORBA Trader), which provides a way to query the KDE infrastructure for specific applications or components. More...

#include <kservicetypetrader.h>

List of all members.


Public Member Functions

KService::List defaultOffers (const QString &serviceType, const QString &constraint=QString()) const
KService::Ptr preferredService (const QString &serviceType) const
KService::List query (const QString &servicetype, const QString &constraint=QString()) const
 ~KServiceTypeTrader ()

Static Public Member Functions

static void applyConstraints (KService::List &lst, const QString &constraint)
template<class T >
static KDE_DEPRECATED T * createInstanceFromQuery (const QString &serviceType, const QString &constraint, QObject *parent, const QStringList &args, int *error=0)
template<class T >
static T * createInstanceFromQuery (const QString &serviceType, QWidget *parentWidget, QObject *parent, const QString &constraint=QString(), const QVariantList &args=QVariantList(), QString *error=0)
template<class T >
static T * createInstanceFromQuery (const QString &serviceType, const QString &constraint=QString(), QObject *parent=0, const QVariantList &args=QVariantList(), QString *error=0)
static KServiceTypeTrader * self ()

Detailed Description

KDE's trader interface (similar to the CORBA Trader), which provides a way to query the KDE infrastructure for specific applications or components.

Basically, KServiceTypeTrader provides a way for an application to query all KDE services (that is, applications, components, plugins) that match a specific set of requirements. This allows to find specific services at run-time without having to hard-code their names and/or paths.

For anything relating to mimetypes (type of files), ignore KServiceTypeTrader and use KMimeTypeTrader instead.

Example
If you want to find all plugins for your application, you would define a KMyApp/Plugin servicetype, and then you can query the trader for it:
 KService::List offers =
     KServiceTypeTrader::self()->query("KMyApp/Plugin");

You can add a constraint in the "trader query language". For instance:

 KServiceTypeTrader::self()->query("KMyApp/Plugin",
                                   "[X-KMyApp-InterfaceVersion] > 15");

Please note that when including property names containing arithmetic operators like - or +, then you have to put brackets around the property name, in order to correctly separate arithmetic operations from the name. So for example a constraint expression like

 X-KMyApp-InterfaceVersion > 4 // wrong!
needs to be written as
 [X-KMyApp-InterfaceVersion] > 4
otherwise it could also be interpreted as Substract the numeric value of the property "KMyApp" and "InterfaceVersion" from the property "X" and make sure it is greater than 4.
Instead of the other meaning, make sure that the numeric value of "X-KMyApp-InterfaceVersion" is greater than 4.

See also:
KMimeTypeTrader, KService

Definition at line 70 of file kservicetypetrader.h.


Constructor & Destructor Documentation

KServiceTypeTrader::~KServiceTypeTrader (  ) 

Standard destructor.

Definition at line 48 of file kservicetypetrader.cpp.


Member Function Documentation

void KServiceTypeTrader::applyConstraints ( KService::List &  lst,
const QString &  constraint 
) [static]

For internal use only.

(public for KMimeTypeTrader)

Definition at line 53 of file kservicetypetrader.cpp.

template<class T >
static KDE_DEPRECATED T* KServiceTypeTrader::createInstanceFromQuery ( const QString &  serviceType,
const QString &  constraint,
QObject *  parent,
const QStringList &  args,
int *  error = 0 
) [inline, static]

Deprecated:
Use createInstanceFromQuery(const QString&, const QString&, QObject*, const QVariantList&, QString*) instead

Definition at line 202 of file kservicetypetrader.h.

template<class T >
static T* KServiceTypeTrader::createInstanceFromQuery ( const QString &  serviceType,
QWidget *  parentWidget,
QObject *  parent,
const QString &  constraint = QString(),
const QVariantList &  args = QVariantList(),
QString *  error = 0 
) [inline, static]

Get a plugin from a trader query.

This method works like createInstanceFromQuery(const QString&, const QString&, QObject*, const QVariantList&, QString*), but you can specify an additional parent widget. This is important for a KPart, for example.

Parameters:
serviceType the type of service for which to find a plugin
parentWidget the parent widget for the plugin
parent the parent object for the part itself
constraint an optional constraint to pass to the trader (see KTrader)
args A list of arguments passed to the service component
error The string passed here will contain an error description.
Returns:
A pointer to the newly created object or a null pointer if the factory was unable to create an object of the given type.

Definition at line 178 of file kservicetypetrader.h.

template<class T >
static T* KServiceTypeTrader::createInstanceFromQuery ( const QString &  serviceType,
const QString &  constraint = QString(),
QObject *  parent = 0,
const QVariantList &  args = QVariantList(),
QString *  error = 0 
) [inline, static]

Get a plugin from a trader query.

Example:

 KMyAppPlugin* plugin = KServiceTypeTrader::createInstanceFromQuery<KMyAppPlugin>( serviceType, QString(), parentObject );
 if ( plugin ) {
     ....
 }

Parameters:
serviceType the type of service for which to find a plugin
constraint an optional constraint to pass to the trader (see KTrader)
parent the parent object for the part itself
args A list of arguments passed to the service component
error The string passed here will contain an error description.
Returns:
A pointer to the newly created object or a null pointer if the factory was unable to create an object of the given type.

Definition at line 153 of file kservicetypetrader.h.

KService::List KServiceTypeTrader::defaultOffers ( const QString &  serviceType,
const QString &  constraint = QString() 
) const

Returns all offers associated with a given servicetype, IGNORING the user preference.

The sorting will be the one coming from the InitialPreference in the .desktop files, and services disabled by the user will still be listed here. This is used for "Revert to defaults" buttons in GUIs.

Definition at line 113 of file kservicetypetrader.cpp.

KService::Ptr KServiceTypeTrader::preferredService ( const QString &  serviceType  )  const

Returns the preferred service for serviceType.

Parameters:
serviceType the service type (e.g. "KMyApp/Plugin")
Returns:
the preferred service, or 0 if no service is available

Definition at line 160 of file kservicetypetrader.cpp.

KService::List KServiceTypeTrader::query ( const QString &  servicetype,
const QString &  constraint = QString() 
) const

The main function in the KServiceTypeTrader class.

It will return a list of services that match your specifications. The only required parameter is the service type. This is something like 'text/plain' or 'text/html'. The constraint parameter is used to limit the possible choices returned based on the constraints you give it.

The constraint language is rather full. The most common keywords are AND, OR, NOT, IN, and EXIST, all used in an almost spoken-word form. An example is:

 (Type == 'Service') and (('KParts/ReadOnlyPart' in ServiceTypes) or (exist Exec))

The keys used in the query (Type, ServiceType, Exec) are all fields found in the .desktop files.

Parameters:
servicetype A service type like 'KMyApp/Plugin' or 'KFilePlugin'.
constraint A constraint to limit the choices returned, QString() to get all services of the given servicetype
Returns:
A list of services that satisfy the query
See also:
http://techbase.kde.org/Development/Tutorials/Services/Traders#The_KTrader_Query_Language

Definition at line 134 of file kservicetypetrader.cpp.

KServiceTypeTrader * KServiceTypeTrader::self (  )  [static]

This is a static pointer to the KServiceTypeTrader singleton.

You will need to use this to access the KServiceTypeTrader functionality since the constructors are protected.

Returns:
Static KServiceTypeTrader instance

Definition at line 37 of file kservicetypetrader.cpp.


The documentation for this class was generated from the following files:
  • kservicetypetrader.h
  • kservicetypetrader.cpp

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