Plasma.DataContainer

KDE 4.2 PyKDE API Reference

- KDE's Python API

# DataContainer Class Reference

`from PyKDE4.plasma import *`

Inherits: QObject
Namespace: Plasma

## Detailed Description

DataContainer plasma/datacontainer.h <Plasma/DataContainer>

A set of data exported via a DataEngine

Plasma.DataContainer wraps the data exported by a DataEngine implementation, providing a generic wrapper for the data.

A DataContainer may have zero or more associated pieces of data which are keyed by strings. The data itself is stored as QVariants. This allows easy and flexible retrieval of the information associated with this object without writing DataContainer or DataEngine specific code in visualizations.

If you are creating your own DataContainer objects (and are passing them to DataEngine.addSource()), you normally just need to listen to the updateRequested() signal (as well as any other methods you might have of being notified of new data) and call setData() to actually update the data. Then you need to either trigger the scheduleSourcesUpdated signal of the parent DataEngine or call checkForUpdate() on the DataContainer.

You also need to set a suitable name for the source with setObjectName(). See DataEngine.addSource() for more information.

Note that there is normally no need to subclass DataContainer, except as a way of encapsulating the data retreival for a source, since all notifications are done via signals rather than virtual methods.

## Signals
| becameUnused (QString source)
| dataUpdated (QString source, Plasma.DataEngine.Data data)
| updateRequested (Plasma.DataContainer source)
## Methods
| __init__ (self, QObject parent=0)
| becameUnused (self, QString source)
| checkForUpdate (self)
| checkUsage (self)
| connectVisualization (self, QObject visualization, long pollingInterval, Plasma.IntervalAlignment alignment)
Plasma.DataEngine.Data | data (self)
| dataUpdated (self, QString source, Plasma.DataEngine.Data data)
| disconnectVisualization (self, QObject visualization)
| removeAllData (self)
| setData (self, QString key, QVariant value)
| setNeedsUpdate (self, bool update=1)
long | timeSinceLastUpdate (self)
| updateRequested (self, Plasma.DataContainer source)
bool | visualizationIsConnected (self, QObject visualization)

## Method Documentation

__init__ | ( | self, |
|  | QObject | parent=0
| ) |  |  |

Constructs a default DataContainer that has no name or data associated with it

becameUnused | ( | self, |
|  | QString | source
| ) |  |  |

Emitted when the last visualization is disconnected.

Note that if this source was created by DataEngine.sourceRequestEvent(), it will be deleted by DataEngine once control returns to the event loop after this signal is emitted.

Parameters:

  | source | the name of the source that became unused

Signal syntax:
  `QObject.connect(source, SIGNAL("becameUnused(const QString&)"), target_slot)`

checkForUpdate | ( |  | self ) |

Checks whether any data has changed and, if so, emits dataUpdated().

checkUsage | ( |  | self ) |

Check if the DataContainer is still in use.

If not the signal "becameUnused" will be emitted.

Warning: The DataContainer may be invalid after calling this function, because a listener to becameUnused() may have deleted it.

connectVisualization | ( | self, |
|  | QObject | visualization,
|  | long | pollingInterval,
|  | Plasma.IntervalAlignment | alignment
| ) |  |  |

Connects an object to this DataContainer.

May be called repeatedly for the same visualization without side effects

Parameters:

  | visualization | the object to connect to this DataContainer
  | pollingInterval | the time in milliseconds between updates
  | alignment | the clock position to align updates to

Plasma.DataEngine.Data data | ( |  | self ) |

Returns the data for this DataContainer

dataUpdated | ( | self, |
|  | QString | source,
|  | Plasma.DataEngine.Data | data
| ) |  |  |

Emitted when the data has been updated, allowing visualizations to reflect the new data.

Note that you should not normally emit this directly. Instead, use checkForUpdates() or the DataEngine.scheduleSourcesUpdated() slot.

Parameters:

  | source | the objectName() of the DataContainer (and hence the name of the source) that updated its data
  | data | the updated data

Signal syntax:
  `QObject.connect(source, SIGNAL("dataUpdated(const QString&, const Data&)"), target_slot)`

disconnectVisualization | ( | self, |
|  | QObject | visualization
| ) |  |  |

Disconnects an object from this DataContainer.

Note that if this source was created by DataEngine.sourceRequestEvent(), it will be deleted by DataEngine once control returns to the event loop.

removeAllData | ( |  | self ) |

Removes all data currently associated with this source

If you call removeAllData() on a DataContainer, you need to either trigger the scheduleSourcesUpdated() slot for the data engine it belongs to or call checkForUpdate() on the DataContainer.

setData | ( | self, |
|  | QString | key,
|  | QVariant | value
| ) |  |  |

Set a value for a key.

This also marks this source as needing to signal an update.

If you call setData() directly on a DataContainer, you need to either trigger the scheduleSourcesUpdated() slot for the data engine it belongs to or call checkForUpdate() on the DataContainer.

Parameters:

  | key | a string used as the key for the data
  | value | a QVariant holding the actual data. If a null or invalid QVariant is passed in and the key currently exists in the data, then the data entry is removed

setNeedsUpdate | ( | self, |
|  | bool | update=1
| ) |  |  |

Indicates that the data should be treated as dirty the next time hasUpdates() is called.

This is needed for the case where updateRequested() is triggered but we don't want to update the data immediately because it has just been updated. The second request won't be fulfilled in this case, because we never updated the data and so never called checkForUpdate(). So we claim it needs an update anyway.

long timeSinceLastUpdate | ( |  | self ) |

Returns how long ago, in msecs, that the data in this container was last updated.

This is used by DataEngine to compress updates that happen more quickly than the minimum polling interval by calling setNeedsUpdate() instead of calling updateSourceEvent() immediately.

updateRequested | ( | self, |
|  | Plasma.DataContainer | source
| ) |  |  |

Emitted when an update is requested.

If a polling interval was passed connectVisualization(), this signal will be emitted every time the interval expires.

Note that if you create your own DataContainer (and pass it to DataEngine.addSource()), you will need to listen to this signal and refresh the data when it is triggered.

Parameters:

  | source | the datacontainer the update was requested for. Useful for classes that update the data for several containers.

Signal syntax:
  `QObject.connect(source, SIGNAL("updateRequested(DataContainer*)"), target_slot)`

bool visualizationIsConnected | ( | self, |
|  | QObject | visualization
| ) |  |  |

Returns:
  true if the visualization is currently connected