This is the base class for vector data providers. More...

#include <qgsvectordataprovider.h>

Inheritance diagram for QgsVectorDataProvider:

Classes
struct	NativeType

Public Types
enum	Capability { NoCapabilities = 0, AddFeatures = 1, DeleteFeatures = 1 << 1, ChangeAttributeValues = 1 << 2, AddAttributes = 1 << 3, DeleteAttributes = 1 << 4, SaveAsShapefile = 1 << 5, CreateSpatialIndex = 1 << 6, SelectAtId = 1 << 7, ChangeGeometries = 1 << 8, SelectGeometryAtId = 1 << 9, RandomSelectGeometryAtId = 1 << 10, SequentialSelectGeometryAtId = 1 << 11, CreateAttributeIndex = 1 << 12, SelectEncoding = 1 << 13, SimplifyGeometries = 1 << 14, SimplifyGeometriesWithTopologicalValidation = 1 << 15 }
	enumeration with capabilities that providers might implement More...
Public Types inherited from QgsDataProvider
enum	DataCapability { NoDataCapabilities = 0, File = 1, Dir = 1 << 1, Database = 1 << 2, Net = 1 << 3 }

Public Member Functions
	QgsVectorDataProvider (QString uri=QString())
	Constructor of the vector provider.
virtual	~QgsVectorDataProvider ()
	Destructor.
virtual QgsAbstractFeatureSource *	featureSource () const
	Return feature source object that can be used for querying provider's data.
virtual QString	storageType () const
	Returns the permanent storage type for this layer as a friendly name.
virtual QgsFeatureIterator	getFeatures (const QgsFeatureRequest &request=QgsFeatureRequest())=0
	Query the provider for features specified in request.
virtual QGis::WkbType	geometryType () const =0
	Get feature type.
virtual long	featureCount () const =0
	Number of features in the layer.
virtual const QgsFields &	fields () const =0
	Return a map of indexes with field names for this layer.
virtual QString	dataComment () const
	Return a short comment for the data that this provider is providing access to (e.g.
virtual QVariant	minimumValue (int index)
	Returns the minimum value of an attribute.
virtual QVariant	maximumValue (int index)
	Returns the maximum value of an attribute.
virtual void	uniqueValues (int index, QList< QVariant > &uniqueValues, int limit=-1)
	Return unique values of an attribute.
virtual void	enumValues (int index, QStringList &enumList)
	Returns the possible enum values of an attribute.
virtual bool	addFeatures (QgsFeatureList &flist)
	Adds a list of features.
virtual bool	deleteFeatures (const QgsFeatureIds &id)
	Deletes one or more features.
virtual bool	addAttributes (const QList< QgsField > &attributes)
	Adds new attributes.
virtual bool	deleteAttributes (const QgsAttributeIds &attributes)
	Deletes existing attributes.
virtual bool	changeAttributeValues (const QgsChangedAttributesMap &attr_map)
	Changes attribute values of existing features.
virtual QVariant	defaultValue (int fieldId)
	Returns the default value for field specified by `fieldId`.
virtual bool	changeGeometryValues (QgsGeometryMap &geometry_map)
	Changes geometries of existing features.
virtual bool	createSpatialIndex ()
	Creates a spatial index on the datasource (if supported by the provider type).
virtual bool	createAttributeIndex (int field)
	Create an attribute index on the datasource.
virtual int	capabilities () const
	Returns a bitmask containing the supported capabilities Note, some capabilities may change depending on whether a spatial filter is active on this provider, so it may be prudent to check this value per intended operation.
QString	capabilitiesString () const
	Returns the above in friendly format.
virtual void	setEncoding (const QString &e)
	Set encoding used for accessing data from layer.
QString	encoding () const
	Get encoding which is used for accessing data.
int	fieldNameIndex (const QString &fieldName) const
	Returns the index of a field name or -1 if the field does not exist.
QMap< QString, int >	fieldNameMap () const
	Return a map where the key is the name of the field and the value is its index.
virtual QgsAttributeList	attributeIndexes ()
	Return list of indexes to fetch all attributes in nextFeature()
virtual QgsAttributeList	pkAttributeIndexes ()
	Return list of indexes of fields that make up the primary key.
virtual QgsAttrPalIndexNameHash	palAttributeIndexNames () const
	Return list of indexes to names for QgsPalLabeling fix.
bool	supportedType (const QgsField &field) const
	check if provider supports type of field
const QList< NativeType > &	nativeTypes () const
	Returns the names of the supported types.
virtual bool	doesStrictFeatureTypeCheck () const
	Returns true if the provider is strict about the type of inserted features (e.g.
bool	hasErrors ()
	Provider has errors to report.
void	clearErrors ()
	Clear recorded errors.
QStringList	errors ()
	Get recorded errors.
virtual bool	isSaveAndLoadStyleToDBSupported ()
	It returns false by default.
Public Member Functions inherited from QgsDataProvider
	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.

Static Public Member Functions
static const QStringList &	availableEncodings ()
	Returns a list of available encodings.
static QVariant	convertValue (QVariant::Type type, QString value)

Static Public Attributes
static const int	EditingCapabilities
	bitmask of all provider's editing capabilities

Protected Member Functions
void	clearMinMaxCache ()
void	fillMinMaxCache ()
void	pushError (QString msg)
Protected Member Functions inherited from QgsDataProvider
void	appendError (const QgsErrorMessage &theMessage)
	Add error message.
void	setError (const QgsError &theError)
	Set error message.

Protected Attributes
bool	mCacheMinMaxDirty
QMap< int, QVariant >	mCacheMinValues
QMap< int, QVariant >	mCacheMaxValues
QTextCodec *	mEncoding
	Encoding.
bool	mFetchFeaturesWithoutGeom
	should provider fetch also features that don't have geometry?
bool	mFetchGeom
	True if geometry should be added to the features in nextFeature calls.
QgsAttributeList	mAttributesToFetch
	List of attribute indices to fetch with nextFeature calls.
QList< NativeType >	mNativeTypes
	The names of the providers native types.
QgsAttrPalIndexNameHash	mAttrPalIndexName
	Old-style mapping of index to name for QgsPalLabeling fix.
Protected Attributes inherited from QgsDataProvider
QDateTime	mTimestamp
	Timestamp of data in the moment when the data were loaded by provider.
QgsError	mError
	Error.

Additional Inherited Members
Signals inherited from QgsDataProvider
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.

Detailed Description

This is the base class for vector data providers.

Data providers abstract the retrieval and writing (where supported) of feature and attribute information from a spatial datasource.

Member Enumeration Documentation

enum QgsVectorDataProvider::Capability

enumeration with capabilities that providers might implement

Enumerator:

NoCapabilities	provider has no capabilities
AddFeatures	allows adding features
DeleteFeatures	allows deletion of features
ChangeAttributeValues	allows modification of attribute values
AddAttributes	allows addition of new attributes (fields)
DeleteAttributes	allows deletion of attributes (fields)
SaveAsShapefile	DEPRECATED - do not use.
CreateSpatialIndex	allows creation of spatial index
SelectAtId	fast access to features using their ID
ChangeGeometries	allows modifications of geometries
SelectGeometryAtId	DEPRECATED - do not use.
RandomSelectGeometryAtId	DEPRECATED - do not use.
SequentialSelectGeometryAtId	DEPRECATED - do not use.
CreateAttributeIndex
SelectEncoding	allows user to select encoding
SimplifyGeometries	supports simplification of geometries on provider side according to a distance tolerance
SimplifyGeometriesWithTopologicalValidation	supports topological simplification of geometries on provider side according to a distance tolerance

Constructor & Destructor Documentation

QgsVectorDataProvider::QgsVectorDataProvider ( QString uri = QString() )

Constructor of the vector provider.

Parameters

uri	uniform resource locator (URI) for a dataset

QgsVectorDataProvider::~QgsVectorDataProvider ( )

virtual

Destructor.

Member Function Documentation

bool QgsVectorDataProvider::addAttributes ( const QList< QgsField > & attributes )

virtual

Adds new attributes.

Parameters

attributes list of new attributes

Returns: true in case of success and false in case of failure

bool QgsVectorDataProvider::addFeatures ( QgsFeatureList & flist )

virtual

Adds a list of features.

Returns: true in case of success and false in case of failure

QgsAttributeList QgsVectorDataProvider::attributeIndexes ( )

virtual

Return list of indexes to fetch all attributes in nextFeature()

const QStringList & QgsVectorDataProvider::availableEncodings ( )

static

Returns a list of available encodings.

int QgsVectorDataProvider::capabilities ( ) const

virtual

Returns a bitmask containing the supported capabilities Note, some capabilities may change depending on whether a spatial filter is active on this provider, so it may be prudent to check this value per intended operation.

QString QgsVectorDataProvider::capabilitiesString ( ) const

Returns the above in friendly format.

bool QgsVectorDataProvider::changeAttributeValues ( const QgsChangedAttributesMap & attr_map )

virtual

Changes attribute values of existing features.

Parameters

attr_map a map containing changed attributes

Returns: true in case of success and false in case of failure

bool QgsVectorDataProvider::changeGeometryValues ( QgsGeometryMap & geometry_map )

virtual

Changes geometries of existing features.

Parameters

geometry_map A QgsGeometryMap whose index contains the feature IDs that will have their geometries changed. The second map parameter being the new geometries themselves

Returns: True in case of success and false in case of failure

void QgsVectorDataProvider::clearErrors ( )

Clear recorded errors.

void QgsVectorDataProvider::clearMinMaxCache ( )

protected

QVariant QgsVectorDataProvider::convertValue	(	QVariant::Type	type,
		QString	value
	)

static

bool QgsVectorDataProvider::createAttributeIndex ( int field )

virtual

Create an attribute index on the datasource.

bool QgsVectorDataProvider::createSpatialIndex ( )

virtual

Creates a spatial index on the datasource (if supported by the provider type).

Returns: true in case of success

QString QgsVectorDataProvider::dataComment ( ) const

virtual

Return a short comment for the data that this provider is providing access to (e.g.

the comment for postgres table).

QVariant QgsVectorDataProvider::defaultValue ( int fieldId )

virtual

Returns the default value for field specified by fieldId.

bool QgsVectorDataProvider::deleteAttributes ( const QgsAttributeIds & attributes )

virtual

Deletes existing attributes.

Parameters

attributes a set containing indices of attributes

Returns: true in case of success and false in case of failure

bool QgsVectorDataProvider::deleteFeatures ( const QgsFeatureIds & id )

virtual

Deletes one or more features.

Parameters

id	list containing feature ids to delete

Returns: true in case of success and false in case of failure

virtual bool QgsVectorDataProvider::doesStrictFeatureTypeCheck ( ) const

inlinevirtual

Returns true if the provider is strict about the type of inserted features (e.g.

no multipolygon in a polygon layer)

QString QgsVectorDataProvider::encoding ( ) const

Get encoding which is used for accessing data.

virtual void QgsVectorDataProvider::enumValues	(	int	index,
		QStringList &	enumList
	)

inlinevirtual

Returns the possible enum values of an attribute.

Returns an empty stringlist if a provider does not support enum types or if the given attribute is not an enum type.

Parameters

index	the index of the attribute
enumList	reference to the list to fill

QStringList QgsVectorDataProvider::errors ( )

Get recorded errors.

virtual long QgsVectorDataProvider::featureCount ( ) const

pure virtual

Number of features in the layer.

Returns: long containing number of features

virtual QgsAbstractFeatureSource* QgsVectorDataProvider::featureSource ( ) const

inlinevirtual

Return feature source object that can be used for querying provider's data.

The returned feature source is independent from provider - any changes to provider's state (e.g. change of subset string) will not be reflected in the feature source, therefore it can be safely used for processing in background without having to care about possible changes within provider that may happen concurrently. Also, even in the case of provider being deleted, any feature source obtained from the provider will be kept alive and working (they are independent and owned by the caller).

Sometimes there are cases when some data needs to be shared between vector data provider and its feature source. In such cases, the implementation must ensure that the data is not susceptible to run condition. For example, if it is possible that both feature source and provider may need reading/writing to some shared data at the same time, some synchronization mechanisms must be used (e.g. mutexes) to prevent data corruption.

Note: added in 2.4

Returns: new instance of QgsAbstractFeatureSource (caller is responsible for deleting it)

int QgsVectorDataProvider::fieldNameIndex ( const QString & fieldName ) const

Returns the index of a field name or -1 if the field does not exist.

QMap< QString, int > QgsVectorDataProvider::fieldNameMap ( ) const

Return a map where the key is the name of the field and the value is its index.

virtual const QgsFields& QgsVectorDataProvider::fields ( ) const

pure virtual

Return a map of indexes with field names for this layer.

Returns: map of fields

See Also: QgsFields

void QgsVectorDataProvider::fillMinMaxCache ( )

protected

virtual QGis::WkbType QgsVectorDataProvider::geometryType ( ) const

pure virtual

Get feature type.

Returns: int representing the feature type

virtual QgsFeatureIterator QgsVectorDataProvider::getFeatures ( const QgsFeatureRequest & request = QgsFeatureRequest() )

pure virtual

Query the provider for features specified in request.

bool QgsVectorDataProvider::hasErrors ( )

Provider has errors to report.

virtual bool QgsVectorDataProvider::isSaveAndLoadStyleToDBSupported ( )

inlinevirtual

It returns false by default.

Must be implemented by providers that support saving and loading styles to db returning true

QVariant QgsVectorDataProvider::maximumValue ( int index )

virtual

Returns the maximum value of an attribute.

Parameters

index the index of the attribute

Default implementation walks all numeric attributes and caches minimal and maximal values. If provider has facilities to retrieve maximal value directly, override this function.

QVariant QgsVectorDataProvider::minimumValue ( int index )

virtual

Returns the minimum value of an attribute.

Parameters

index the index of the attribute

Default implementation walks all numeric attributes and caches minimal and maximal values. If provider has facilities to retrieve minimal value directly, override this function.

const QList< QgsVectorDataProvider::NativeType > & QgsVectorDataProvider::nativeTypes ( ) const

Returns the names of the supported types.

virtual QgsAttrPalIndexNameHash QgsVectorDataProvider::palAttributeIndexNames ( ) const

inlinevirtual

Return list of indexes to names for QgsPalLabeling fix.

virtual QgsAttributeList QgsVectorDataProvider::pkAttributeIndexes ( )

inlinevirtual

Return list of indexes of fields that make up the primary key.

void QgsVectorDataProvider::pushError ( QString msg )

protected

void QgsVectorDataProvider::setEncoding ( const QString & e )

virtual

Set encoding used for accessing data from layer.

QString QgsVectorDataProvider::storageType ( ) const

virtual

Returns the permanent storage type for this layer as a friendly name.

bool QgsVectorDataProvider::supportedType ( const QgsField & field ) const

check if provider supports type of field

void QgsVectorDataProvider::uniqueValues	(	int	index,
		QList< QVariant > &	uniqueValues,
		int	limit = `-1`
	)

virtual

Return unique values of an attribute.

Parameters

index	the index of the attribute
uniqueValues	values reference to the list to fill
limit	maxmum number of the values to return

Default implementation simply iterates the features

Member Data Documentation

const int QgsVectorDataProvider::EditingCapabilities

static

Initial value:

AddFeatures | DeleteFeatures |

ChangeAttributeValues | ChangeGeometries | AddAttributes | DeleteAttributes

bitmask of all provider's editing capabilities

QgsAttributeList QgsVectorDataProvider::mAttributesToFetch

protected

List of attribute indices to fetch with nextFeature calls.

QgsAttrPalIndexNameHash QgsVectorDataProvider::mAttrPalIndexName

protected

Old-style mapping of index to name for QgsPalLabeling fix.

QMap<int, QVariant> QgsVectorDataProvider::mCacheMaxValues

protected

bool QgsVectorDataProvider::mCacheMinMaxDirty

protected

QMap<int, QVariant> QgsVectorDataProvider::mCacheMinValues

protected

QTextCodec* QgsVectorDataProvider::mEncoding

protected

Encoding.

bool QgsVectorDataProvider::mFetchFeaturesWithoutGeom

protected

should provider fetch also features that don't have geometry?

bool QgsVectorDataProvider::mFetchGeom

protected

True if geometry should be added to the features in nextFeature calls.

QList< NativeType > QgsVectorDataProvider::mNativeTypes

protected

The names of the providers native types.

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

/tmp/buildd/qgis-2.6.0+wheezy1/src/core/qgsvectordataprovider.h
/tmp/buildd/qgis-2.6.0+wheezy1/src/core/qgsvectordataprovider.cpp

Classes

Public Types

Public Member Functions

Static Public Member Functions

Static Public Attributes

Protected Member Functions

Protected Attributes

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation