QgsDataProvider Class Reference

Abstract base class for spatial data provider implementations. More...

#include <qgsdataprovider.h>

Inheritance diagram for QgsDataProvider:

Public Types
enum	DataCapability {   NoDataCapabilities = 0, File = 1, Dir = 1 << 1, Database = 1 << 2,   Net = 1 << 3 }

Signals
void	fullExtentCalculated ()
	This is emitted whenever the worker thread has fully calculated the PostGIS extents for this layer, and its event has been received by this provider.
void	dataChanged ()
	This is emitted whenever an asynchronous operation has finished and the data should be redrawn.
void	dataChanged (int changed)
	This is emitted whenever data or metadata (e.g.

Public Member Functions
	QgsDataProvider (QString const &uri="")
virtual	~QgsDataProvider ()
	We need this so the subclass destructors get called.
virtual QgsCoordinateReferenceSystem	crs ()=0
virtual void	setDataSourceUri (const QString &uri)
	Set the data source specification.
virtual QString	dataSourceUri () const
	Get the data source specification.
virtual QgsRectangle	extent ()=0
	Get the extent of the layer.
virtual bool	isValid ()=0
	Returns true if this is a valid layer.
virtual void	updateExtents ()
	Update the extents of the layer.
virtual bool	setSubsetString (QString subset, bool updateFeatureCount=true)
	Set the subset string used to create a subset of features in the layer.
virtual bool	supportsSubsetString ()
	provider supports setting of subset strings
virtual QString	subsetString ()
	Returns the subset definition string (typically sql) currently in use by the layer and used by the provider to limit the feature set.
virtual QStringList	subLayers () const
	Sub-layers handled by this provider, in order from bottom to top.
virtual QStringList	subLayerStyles () const
	Sub-layer styles for each sub-layer handled by this provider, in order from bottom to top.
virtual uint	subLayerCount () const
	return the number of layers for the current data source
virtual void	setLayerOrder (const QStringList &layers)
	Reorder the list of layer names to be rendered by this provider (in order from bottom to top)
virtual void	setSubLayerVisibility (const QString &name, bool vis)
	Set the visibility of the given sublayer name.
virtual QString	name () const =0
	return a provider name
virtual QString	description () const =0
	return description
virtual QString	fileVectorFilters () const
	return vector file filter string
virtual QString	fileRasterFilters () const
	return raster file filter string
virtual void	reloadData ()
	Reloads the data from the source.
virtual QDateTime	timestamp () const
	Time stamp of data source in the moment when data/metadata were loaded by provider.
virtual QDateTime	dataTimestamp () const
	Current time stamp of data source.
virtual QgsError	error () const
	Get current status error.

Protected Member Functions
void	appendError (const QgsErrorMessage &theMessage)
	Add error message.
void	setError (const QgsError &theError)
	Set error message.

Protected Attributes
QDateTime	mTimestamp
	Timestamp of data in the moment when the data were loaded by provider.
QgsError	mError
	Error.

Detailed Description

Abstract base class for spatial data provider implementations.

Author

Gary E.Sherman

This object needs to inherit from QObject to enable event processing in the Postgres/PostGIS provider (QgsPostgresProvider). It is called here so that this vtable and the vtable for QgsPostgresProvider don't get misaligned - the QgsVectorLayer class factory (which refers to generic QgsVectorDataProvider's) depends on it.

Member Enumeration Documentation

enum QgsDataProvider::DataCapability

Enumerator:

NoDataCapabilities
File
Dir
Database
Net

Constructor & Destructor Documentation

QgsDataProvider::QgsDataProvider ( QString const &  uri = "" )

inline

virtual QgsDataProvider::~QgsDataProvider ( )

inlinevirtual

We need this so the subclass destructors get called.

Member Function Documentation

void QgsDataProvider::appendError ( const QgsErrorMessage &  theMessage )

inlineprotected

Add error message.

virtual QgsCoordinateReferenceSystem QgsDataProvider::crs ( )

pure virtual

Get the QgsCoordinateReferenceSystem for this layer

Note

Must be reimplemented by each provider. If the provider isn't capable of returning its projection an empty srs will be return, ti will return 0

void QgsDataProvider::dataChanged ( )

signal

This is emitted whenever an asynchronous operation has finished and the data should be redrawn.

void QgsDataProvider::dataChanged ( int  changed )

signal

This is emitted whenever data or metadata (e.g.

color table, extent) has changed

Parameters

changed

binary combination of changes

virtual QString QgsDataProvider::dataSourceUri ( ) const

inlinevirtual

Get the data source specification.

This may be a path or database connection string

Returns

data source specification

virtual QDateTime QgsDataProvider::dataTimestamp ( ) const

inlinevirtual

Current time stamp of data source.

Reimplemented in QgsRasterDataProvider.

virtual QString QgsDataProvider::description ( ) const

pure virtual

return description

Return a terse string describing what the provider is.

Note

Instead of being pure virtual, might be better to generalize this behavior and presume that none of the sub-classes are going to do anything strange with regards to their name or description?

virtual QgsError QgsDataProvider::error ( ) const

inlinevirtual

Get current status error.

This error describes some principal problem for which provider cannot work and thus is not valid. It is not last error after accessing data by block(), identify() etc.

virtual QgsRectangle QgsDataProvider::extent ( )

pure virtual

Get the extent of the layer.

Returns

QgsRectangle containing the extent of the layer

Implemented in QgsRasterDataProvider.

virtual QString QgsDataProvider::fileRasterFilters ( ) const

inlinevirtual

return raster file filter string

Returns a string suitable for a QFileDialog of raster file formats supported by the data provider. Naturally this will be an empty string for those data providers that do not deal with plain files, such as databases and servers.

Note

It'd be nice to eventually be raster/vector neutral.

virtual QString QgsDataProvider::fileVectorFilters ( ) const

inlinevirtual

return vector file filter string

Returns a string suitable for a QFileDialog of vector file formats supported by the data provider. Naturally this will be an empty string for those data providers that do not deal with plain files, such as databases and servers.

Note

It'd be nice to eventually be raster/vector neutral.

void QgsDataProvider::fullExtentCalculated ( )

signal

This is emitted whenever the worker thread has fully calculated the PostGIS extents for this layer, and its event has been received by this provider.

virtual bool QgsDataProvider::isValid ( )

pure virtual

Returns true if this is a valid layer.

It is up to individual providers to determine what constitutes a valid layer

virtual QString QgsDataProvider::name ( ) const

pure virtual

return a provider name

Essentially just returns the provider key. Should be used to build file dialogs so that providers can be shown with their supported types. Thus if more than one provider supports a given format, the user is able to select a specific provider to open that file.

Note

Instead of being pure virtual, might be better to generalize this behavior and presume that none of the sub-classes are going to do anything strange with regards to their name or description?

virtual void QgsDataProvider::reloadData ( )

inlinevirtual

Reloads the data from the source.

Needs to be implemented by providers with data caches to synchronize with changes in the data source

virtual void QgsDataProvider::setDataSourceUri ( const QString &  uri )

inlinevirtual

Set the data source specification.

This may be a path or database connection string

Parameters

uri	source specification

void QgsDataProvider::setError ( const QgsError &  theError )

inlineprotected

Set error message.

virtual void QgsDataProvider::setLayerOrder ( const QStringList &  layers )

inlinevirtual

Reorder the list of layer names to be rendered by this provider (in order from bottom to top)

Note

layers must have been previously added.

virtual void QgsDataProvider::setSubLayerVisibility ( const QString &  name, bool  vis  )

inlinevirtual

Set the visibility of the given sublayer name.

virtual bool QgsDataProvider::setSubsetString ( QString  subset, bool  updateFeatureCount = true  )

inlinevirtual

Set the subset string used to create a subset of features in the layer.

This may be a sql where clause or any other string that can be used by the data provider to create a subset. Must be implemented in the dataprovider.

virtual uint QgsDataProvider::subLayerCount ( ) const

inlinevirtual

return the number of layers for the current data source

virtual QStringList QgsDataProvider::subLayers ( ) const

inlinevirtual

Sub-layers handled by this provider, in order from bottom to top.

Sub-layers are used when the provider's source can combine layers it knows about in some way before it hands them off to the provider.

Reimplemented in QgsRasterDataProvider.

virtual QStringList QgsDataProvider::subLayerStyles ( ) const

inlinevirtual

Sub-layer styles for each sub-layer handled by this provider, in order from bottom to top.

Sub-layer styles are used to abstract the way the provider's source can symbolise layers in some way at the server, before it serves them to the provider.

virtual QString QgsDataProvider::subsetString ( )

inlinevirtual

Returns the subset definition string (typically sql) currently in use by the layer and used by the provider to limit the feature set.

Must be overridden in the dataprovider, otherwise returns a null QString.

virtual bool QgsDataProvider::supportsSubsetString ( )

inlinevirtual

provider supports setting of subset strings

virtual QDateTime QgsDataProvider::timestamp ( ) const

inlinevirtual

Time stamp of data source in the moment when data/metadata were loaded by provider.

Reimplemented in QgsRasterDataProvider.

virtual void QgsDataProvider::updateExtents ( )

inlinevirtual

Update the extents of the layer.

Not implemented by default

Member Data Documentation

QgsError QgsDataProvider::mError

protected

Error.

QDateTime QgsDataProvider::mTimestamp

protected

Timestamp of data in the moment when the data were loaded by provider.

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The documentation for this class was generated from the following file:

• /tmp/buildd/qgis-2.6.0+wheezy1/src/core/qgsdataprovider.h