Detailed Description
The QValueSpacePublisher class allows applications to publish values in the Value Space.
When multiple Value Space layers are available QValueSpacePublisher only publishes values to the layer with the highest priority. The layers that QValueSpacePublisher can access can be limited by specifying either a filter or a QUuid at construction time.
The lifetime of values published in the Value Space is specified by the particular Value Space layer that the value is published in. For details on the different behaviors see QValueSpace::LayerOption.
Once a value is published all applications in the system will have read access to it via the QValueSpaceSubscriber class.
Although, logically, the Value Space is a simple collection of hierarchical paths, these paths can conceptually be visualized as a set of objects with attributes. For example, rather than viewing the following list as 12 distinct Value Space paths:
/Device/Network/Interfaces/eth0/Name
/Device/Network/Interfaces/eth0/Type
/Device/Network/Interfaces/eth0/Status
/Device/Network/Interfaces/eth0/BytesSent
/Device/Network/Interfaces/eth0/BytesReceived
/Device/Network/Interfaces/eth0/Time
/Device/Network/Interfaces/ppp0/Name
/Device/Network/Interfaces/ppp0/Type
/Device/Network/Interfaces/ppp0/Status
/Device/Network/Interfaces/ppp0/BytesSent
/Device/Network/Interfaces/ppp0/BytesReceived
/Device/Network/Interfaces/ppp0/Time
it can be thought of as describing two Value Space objects, { /Device/Network/Interfaces/eth0, /Device/Network/Interfaces/ppp0 }, each with the six attributes {Name, Type, Status, BytesSent, BytesReceived, Time}. The QValueSpacePublisher class encapsulates this abstraction.
For performance reasons the setting of and removing of attributes is buffered internally by the QValueSpacePublisher and applied as a batch sometime later. Normally this occurs the next time the application enters the Qt event loop, but this behavior should not be relied upon. If an application must synchronize with others, the QValueSpacePublisher::sync() and QValueSpacePublisher::syncAll() functions can be used to force the application of changes. This call is generally unnecessary, and should be used sparingly to prevent unnecessary load on the system.
Member Function Documentation
QValueSpacePublisher::QValueSpacePublisher(const QString & path, QObject * parent = 0)
Constructs a QValueSpacePublisher with the specified parent that publishes values under path.
QValueSpacePublisher::QValueSpacePublisher(QValueSpace::LayerOptions filter, const QString & path, QObject * parent = 0)
Constructs a QValueSpacePublisher with the specified parent that publishes values under path. The filter parameter is used to limit which layer this QValueSpacePublisher will access.
The constructed Value Space publisher will access the layer with the highest priority that matches filter and for which path is a valid path.
If no suitable layer is found, the constructed QValueSpacePublisher will be unconnected.
See also isConnected().
QValueSpacePublisher::QValueSpacePublisher(const QUuid & uuid, const QString & path, QObject * parent = 0)
Constructs a QValueSpacePublisher with the specified parent that publishes values under path. Only the layer identified by uuid will be accessed by this publisher.
Use of this constructor is not platform agnostic. If possible use one of the constructors that take a QValueSpace::LayerOptions parameter instead.
If a layer with a matching uuid is not found, the constructed QValueSpacePublisher will be unconnected.
See also isConnected().
QValueSpacePublisher::~QValueSpacePublisher() [virtual]
Destroys the QValueSpacePublisher. This will remove all values published by this publisher in non-permanent layers.
void QValueSpacePublisher::connectNotify(const QMetaMethod & signal) [virtual protected]
Reimplemented from QObject::connectNotify().
void QValueSpacePublisher::interestChanged(const QString & attribute, bool interested) [signal]
Signal that is emitted when interest in attribute changes. If interested is true at least on QValueSpaceSubscriber is interested in the value of attribute.
bool QValueSpacePublisher::isConnected() const
Returns true if this QValueSpacePublisher is connected to an available layer; otherwise returns false.
QString QValueSpacePublisher::path() const
Returns the path that this QValueSpacePublisher refers to.
void QValueSpacePublisher::resetValue(const QString & name) [slot]
Removes the value name and all sub-attributes from the system.
For example:
QValueSpacePublisher publisher("/Device");
publisher.setValue("State", "Starting");
publisher.setValue("State/Memory", "1000");
publisher.sync();
publisher.resetValue("State");
publisher.sync();
void QValueSpacePublisher::setValue(const QString & name, const QVariant & data) [slot]
Sets the value name on the publisher to data. If name is empty, this call will set the value of this publisher's path.
For example:
QValueSpacePublisher publisher("/Device");
publisher.setValue("State", "Starting");
publisher.sync();
void QValueSpacePublisher::sync()
Forcibly sync all Value Space publisher using the same layer as this publisher.
For performance reasons attribute changes are batched internally by QValueSpacePublisher instances. In cases where the visibility of changes must be synchronized with other processes, calling this function will flush these batches. By the time this function returns, all other processes in the system will be able to see the attribute changes.
Generally, calling this function is unnecessary.
