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, TransactionSupport = 1 << 16 }
	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 bool	addAttributes (const QList< QgsField > &attributes)
	Adds new attributes.
virtual bool	addFeatures (QgsFeatureList &flist)
	Adds a list of features.
virtual QgsAttributeList	attributeIndexes ()
	Return list of indexes to fetch all attributes in nextFeature()
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 bool	changeAttributeValues (const QgsChangedAttributesMap &attr_map)
	Changes attribute values of existing features.
virtual bool	changeGeometryValues (QgsGeometryMap &geometry_map)
	Changes geometries of existing features.
void	clearErrors ()
	Clear recorded errors.
virtual bool	createAttributeIndex (int field)
	Create an attribute index on the datasource.
virtual bool	createSpatialIndex ()
	Creates a spatial index on the datasource (if supported by the provider type).
virtual QString	dataComment () const
	Return a short comment for the data that this provider is providing access to (e.g.
virtual QVariant	defaultValue (int fieldId)
	Returns the default value for field specified by `fieldId`.
virtual bool	deleteAttributes (const QgsAttributeIds &attributes)
	Deletes existing attributes.
virtual bool	deleteFeatures (const QgsFeatureIds &id)
	Deletes one or more features.
virtual bool	doesStrictFeatureTypeCheck () const
	Returns true if the provider is strict about the type of inserted features (e.g.
QString	encoding () const
	Get encoding which is used for accessing data.
virtual void	enumValues (int index, QStringList &enumList)
	Returns the possible enum values of an attribute.
QStringList	errors ()
	Get recorded errors.
virtual long	featureCount () const =0
	Number of features in the layer.
virtual QgsAbstractFeatureSource *	featureSource () const
	Return feature source object that can be used for querying provider's 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 const QgsFields &	fields () const =0
	Return a map of indexes with field names for this layer.
virtual QGis::WkbType	geometryType () const =0
	Get feature type.
virtual QgsFeatureIterator	getFeatures (const QgsFeatureRequest &request=QgsFeatureRequest())=0
	Query the provider for features specified in request.
bool	hasErrors ()
	Provider has errors to report.
virtual bool	isSaveAndLoadStyleToDBSupported ()
	It returns false by default.
virtual QVariant	maximumValue (int index)
	Returns the maximum value of an attribute.
virtual QVariant	minimumValue (int index)
	Returns the minimum value of an attribute.
const QList< NativeType > &	nativeTypes () const
	Returns the names of the supported types.
virtual QgsAttrPalIndexNameHash	palAttributeIndexNames () const
	Return list of indexes to names for QgsPalLabeling fix.
virtual QgsAttributeList	pkAttributeIndexes ()
	Return list of indexes of fields that make up the primary key.
virtual void	setEncoding (const QString &e)
	Set encoding used for accessing data from layer.
virtual QString	storageType () const
	Returns the permanent storage type for this layer as a friendly name.
bool	supportedType (const QgsField &field) const
	check if provider supports type of field
virtual QgsTransaction *	transaction () const
	Returns the transaction this data provider is included in, if any.
virtual void	uniqueValues (int index, QList< QVariant > &uniqueValues, int limit=-1)
	Return unique values of an attribute.
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 QString	dataSourceUri () const
	Get the data source specification.
virtual QDateTime	dataTimestamp () const
	Current time stamp of data source.
virtual QString	description () const =0
	return description
virtual QgsError	error () const
	Get current status error.
virtual QgsRectangle	extent ()=0
	Get the extent of the layer.
virtual QString	fileRasterFilters () const
	return raster file filter string
virtual QString	fileVectorFilters () const
	return vector file filter string
virtual bool	isValid ()=0
	Returns true if this is a valid layer.
virtual QString	name () const =0
	return a provider name
virtual void	reloadData ()
	Reloads the data from the source.
virtual void	setDataSourceUri (const QString &uri)
	Set the data source specification.
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 bool	setSubsetString (QString subset, bool updateFeatureCount=true)
	Set the subset string used to create a subset of features in the layer.
virtual uint	subLayerCount () const
	return the number of layers for the current data source
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 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 bool	supportsSubsetString ()
	provider supports setting of subset strings
virtual QDateTime	timestamp () const
	Time stamp of data source in the moment when data/metadata were loaded by provider.
virtual void	updateExtents ()
	Update the extents of the layer.

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
QgsAttributeList	mAttributesToFetch
	List of attribute indices to fetch with nextFeature calls.
QgsAttrPalIndexNameHash	mAttrPalIndexName
	Old-style mapping of index to name for QgsPalLabeling fix.
QMap< int, QVariant >	mCacheMaxValues
bool	mCacheMinMaxDirty
QMap< int, QVariant >	mCacheMinValues
QTextCodec *	mEncoding
	Encoding.
QList< NativeType >	mNativeTypes
	The names of the providers native types.
Protected Attributes inherited from QgsDataProvider
QgsError	mError
	Error.
QDateTime	mTimestamp
	Timestamp of data in the moment when the data were loaded by provider.

Friends
class	QgsTransaction

Additional Inherited Members
Signals inherited from QgsDataProvider
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.
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.

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.

Definition at line 49 of file qgsvectordataprovider.h.

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
TransactionSupport	supports transactions

Definition at line 61 of file qgsvectordataprovider.h.

Constructor & Destructor Documentation

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

Constructor of the vector provider.

Parameters

uri	uniform resource locator (URI) for a dataset

Definition at line 30 of file qgsvectordataprovider.cpp.

QgsVectorDataProvider::~QgsVectorDataProvider ( )

virtual

Destructor.

Definition at line 40 of file qgsvectordataprovider.cpp.

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

Definition at line 66 of file qgsvectordataprovider.cpp.

bool QgsVectorDataProvider::addFeatures ( QgsFeatureList & flist )

virtual

Adds a list of features.

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

Definition at line 54 of file qgsvectordataprovider.cpp.

QgsAttributeList QgsVectorDataProvider::attributeIndexes ( )

virtual

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

Definition at line 241 of file qgsvectordataprovider.cpp.

const QStringList & QgsVectorDataProvider::availableEncodings ( )

static

Returns a list of available encodings.

Definition at line 467 of file qgsvectordataprovider.cpp.

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.

Definition at line 107 of file qgsvectordataprovider.cpp.

QString QgsVectorDataProvider::capabilitiesString ( ) const

Returns the above in friendly format.

Definition at line 142 of file qgsvectordataprovider.cpp.

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

Definition at line 78 of file qgsvectordataprovider.cpp.

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

Definition at line 90 of file qgsvectordataprovider.cpp.

void QgsVectorDataProvider::clearErrors ( )

Clear recorded errors.

Definition at line 530 of file qgsvectordataprovider.cpp.

void QgsVectorDataProvider::clearMinMaxCache ( )

protected

Definition at line 374 of file qgsvectordataprovider.cpp.

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

static

Definition at line 452 of file qgsvectordataprovider.cpp.

bool QgsVectorDataProvider::createAttributeIndex ( int field )

virtual

Create an attribute index on the datasource.

Definition at line 101 of file qgsvectordataprovider.cpp.

bool QgsVectorDataProvider::createSpatialIndex ( )

virtual

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

Returns: true in case of success

Definition at line 96 of file qgsvectordataprovider.cpp.

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).

Definition at line 49 of file qgsvectordataprovider.cpp.

QVariant QgsVectorDataProvider::defaultValue ( int fieldId )

virtual

Returns the default value for field specified by fieldId.

Definition at line 84 of file qgsvectordataprovider.cpp.

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

Definition at line 72 of file qgsvectordataprovider.cpp.

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

Definition at line 60 of file qgsvectordataprovider.cpp.

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)

Definition at line 338 of file qgsvectordataprovider.h.

QString QgsVectorDataProvider::encoding ( ) const

Get encoding which is used for accessing data.

Definition at line 132 of file qgsvectordataprovider.cpp.

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

Definition at line 204 of file qgsvectordataprovider.h.

QStringList QgsVectorDataProvider::errors ( )

Get recorded errors.

Definition at line 540 of file qgsvectordataprovider.cpp.

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)

Definition at line 131 of file qgsvectordataprovider.h.

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

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

Definition at line 214 of file qgsvectordataprovider.cpp.

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

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

Definition at line 228 of file qgsvectordataprovider.cpp.

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

Definition at line 379 of file qgsvectordataprovider.cpp.

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.

Definition at line 535 of file qgsvectordataprovider.cpp.

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

Definition at line 363 of file qgsvectordataprovider.h.

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.

Definition at line 335 of file qgsvectordataprovider.cpp.

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.

Definition at line 319 of file qgsvectordataprovider.cpp.

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

Returns the names of the supported types.

Definition at line 246 of file qgsvectordataprovider.cpp.

virtual QgsAttrPalIndexNameHash QgsVectorDataProvider::palAttributeIndexNames ( ) const

inlinevirtual

Return list of indexes to names for QgsPalLabeling fix.

Definition at line 308 of file qgsvectordataprovider.h.

virtual QgsAttributeList QgsVectorDataProvider::pkAttributeIndexes ( )

inlinevirtual

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

Definition at line 303 of file qgsvectordataprovider.h.

void QgsVectorDataProvider::pushError ( QString msg )

protected

Definition at line 545 of file qgsvectordataprovider.cpp.

void QgsVectorDataProvider::setEncoding ( const QString & e )

virtual

Set encoding used for accessing data from layer.

Definition at line 113 of file qgsvectordataprovider.cpp.

QString QgsVectorDataProvider::storageType ( ) const

virtual

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

Definition at line 44 of file qgsvectordataprovider.cpp.

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

check if provider supports type of field

Definition at line 251 of file qgsvectordataprovider.cpp.

virtual QgsTransaction* QgsVectorDataProvider::transaction ( ) const

inlinevirtual

Returns the transaction this data provider is included in, if any.

Definition at line 370 of file qgsvectordataprovider.h.

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

Definition at line 351 of file qgsvectordataprovider.cpp.

Friends And Related Function Documentation

friend class QgsTransaction

friend

Definition at line 53 of file qgsvectordataprovider.h.

Member Data Documentation

const int QgsVectorDataProvider::EditingCapabilities

static

Initial value:

AddFeatures | DeleteFeatures |

ChangeAttributeValues | ChangeGeometries | AddAttributes | DeleteAttributes

bitmask of all provider's editing capabilities

Definition at line 101 of file qgsvectordataprovider.h.

QgsAttributeList QgsVectorDataProvider::mAttributesToFetch

protected

List of attribute indices to fetch with nextFeature calls.

Definition at line 383 of file qgsvectordataprovider.h.

QgsAttrPalIndexNameHash QgsVectorDataProvider::mAttrPalIndexName

protected

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

Definition at line 391 of file qgsvectordataprovider.h.

QMap<int, QVariant> QgsVectorDataProvider::mCacheMaxValues

protected

Definition at line 377 of file qgsvectordataprovider.h.

bool QgsVectorDataProvider::mCacheMinMaxDirty

protected

Definition at line 376 of file qgsvectordataprovider.h.

QMap<int, QVariant> QgsVectorDataProvider::mCacheMinValues

protected

Definition at line 377 of file qgsvectordataprovider.h.

QTextCodec* QgsVectorDataProvider::mEncoding

protected

Encoding.

Definition at line 380 of file qgsvectordataprovider.h.

QList< NativeType > QgsVectorDataProvider::mNativeTypes

protected

The names of the providers native types.

Definition at line 386 of file qgsvectordataprovider.h.

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

/tmp/buildd/qgis-2.8.2+12wheezy/src/core/qgsvectordataprovider.h
/tmp/buildd/qgis-2.8.2+12wheezy/src/core/qgsvectordataprovider.cpp

Classes

Public Types

Public Member Functions

Static Public Member Functions

Static Public Attributes

Protected Member Functions

Protected Attributes

Friends

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Friends And Related Function Documentation

Member Data Documentation