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QgsDataProvider Class Referenceabstract

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

#include <qgsdataprovider.h>

Inheritance diagram for QgsDataProvider:
Inheritance graph
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Public Types

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

Signals

void dataChanged ()
 This is emitted whenever an asynchronous operation has finished and the data should be redrawn. More...
 
void dataChanged (int changed)
 This is emitted whenever data or metadata (e.g. More...
 
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. More...
 

Public Member Functions

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

Protected Member Functions

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

Protected Attributes

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

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.

Definition at line 46 of file qgsdataprovider.h.

Constructor & Destructor Documentation

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

Definition at line 63 of file qgsdataprovider.h.

virtual QgsDataProvider::~QgsDataProvider ( )
inlinevirtual

We need this so the subclass destructors get called.

Definition at line 70 of file qgsdataprovider.h.

Member Function Documentation

void QgsDataProvider::appendError ( const QgsErrorMessage theMessage)
inlineprotected

Add error message.

Definition at line 330 of file qgsdataprovider.h.

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
changedbinary 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

Definition at line 96 of file qgsdataprovider.h.

virtual QDateTime QgsDataProvider::dataTimestamp ( ) const
inlinevirtual

Current time stamp of data source.

Reimplemented in QgsRasterDataProvider.

Definition at line 291 of file qgsdataprovider.h.

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.

Definition at line 297 of file qgsdataprovider.h.

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.

Definition at line 278 of file qgsdataprovider.h.

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.

Definition at line 261 of file qgsdataprovider.h.

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

Definition at line 285 of file qgsdataprovider.h.

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

Set the data source specification.

This may be a path or database connection string

Parameters
urisource specification

Definition at line 86 of file qgsdataprovider.h.

void QgsDataProvider::setError ( const QgsError theError)
inlineprotected

Set error message.

Definition at line 333 of file qgsdataprovider.h.

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.

Definition at line 194 of file qgsdataprovider.h.

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

Set the visibility of the given sublayer name.

Definition at line 208 of file qgsdataprovider.h.

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.

Definition at line 131 of file qgsdataprovider.h.

virtual uint QgsDataProvider::subLayerCount ( ) const
inlinevirtual

return the number of layers for the current data source

Definition at line 183 of file qgsdataprovider.h.

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.

Definition at line 161 of file qgsdataprovider.h.

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.

Definition at line 174 of file qgsdataprovider.h.

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.

Definition at line 149 of file qgsdataprovider.h.

virtual bool QgsDataProvider::supportsSubsetString ( )
inlinevirtual

provider supports setting of subset strings

Definition at line 141 of file qgsdataprovider.h.

virtual QDateTime QgsDataProvider::timestamp ( ) const
inlinevirtual

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

Reimplemented in QgsRasterDataProvider.

Definition at line 288 of file qgsdataprovider.h.

virtual void QgsDataProvider::updateExtents ( )
inlinevirtual

Update the extents of the layer.

Not implemented by default

Definition at line 119 of file qgsdataprovider.h.

Member Data Documentation

QgsError QgsDataProvider::mError
protected

Error.

Definition at line 327 of file qgsdataprovider.h.

QDateTime QgsDataProvider::mTimestamp
protected

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

Definition at line 324 of file qgsdataprovider.h.


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