Service Framework QML Plugin

Service

The Service element provides QML with functionality reflecting the QServiceInterfaceDescriptor class which represents the details of a single service registered on the service framework system. This element also allows the service to be loaded so that it will return a QObject reference of the instantiated service object. If this element is used on its own and not in conjunction to the ServiceList element below, it will represent the default interface at the specified interface name, which is the most convenient use-case of the QML plugin. The code snippet below demonstrates a typical way to load an interface in QML.

 import QtQuick 2.0
 import Qt.serviceframework 5.0

 // ...
 property variant myObject: 0

 Service {
     id: myService
     interfaceName: "com.nokia.qt.examples.ExampleService"

     Component.onCompleted: {
         myObject = myService.serviceObject;
     }
 }

In the above code we use a variant to store the QObject reference provided by the Service::serviceObject. In this case it will be an instance of the default service found at the interface address "com.nokia.qt.examples.ExampleService". The code inside the QML component element is recommended so that the variable myObject holds a valid object instance which can be used throughout the entire QML script.

This element also provides several readable properties about the service interface. A useful one is the Service::valid property which will help debug if the system has found a valid default interface descriptor at the specified interface name. The plugin also allows connecting to signals provided by the service. Here is a typical example of receiving service signals within QML for the above code.

 Connections {
     target: myObject
     ignoreUnknownSignals: true

     onMySignal: {
         // do something
     }
 }

Note the usage of the ignoreUnkownSignals attribute which is useful for ignoring uknown signals, especially in the case where Service::serviceObject has not been called yet or provides an invalid interface.

Once a valid service instance has been obtained its methods and properties can be called and accessed as if it were normal QObject in QML. The service framework example Declarative Dialer Example demonstrates the use of the QML plugin.

 ServiceList {
     id: myServiceList
     serviceName: "MyExampleService"
     interfaceName: "com.nokia.qt.examples.ExampleService"
     versionMatch: ServiceList.Exact
     majorVersion: 1
     minorVersion: 3
 }

 ListView {
     id: myListView
     model: myServiceList.services
     delegate: myDelegate
     // ...
 }