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

#include <qgsdataprovider.h>

Inheritance diagram for QgsDataProvider:

Classes
struct	PreviewContext
	Stores settings related to the context in which a preview job runs. More...

struct	ProviderOptions
	Setting options for creating vector data providers. More...

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

enum	ProviderProperty { EvaluateDefaultValues, CustomData = 3000 }
	Properties are used to pass custom configuration options into data providers. More...

Signals
void	dataChanged ()
	This is emitted whenever an asynchronous operation has finished and the data should be redrawn. 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...

void	notify (const QString &msg)
	Emitted when datasource issues a notification. More...

Public Member Functions
	QgsDataProvider (const QString &uri=QString(), const QgsDataProvider::ProviderOptions &options=QgsDataProvider::ProviderOptions())
	Create a new dataprovider with the specified in the uri. More...

virtual QgsCoordinateReferenceSystem	crs () const =0
	Returns the coordinate system for the data source. More...

virtual QString	dataSourceUri (bool expandAuthConfig=false) const
	Gets the data source specification. More...

virtual QDateTime	dataTimestamp () const
	Current time stamp of data source. More...

virtual QString	description () const =0
	Returns description. More...

virtual bool	enterUpdateMode ()
	Enter update mode. More...

virtual QgsError	error () const
	Gets current status error. More...

virtual QgsRectangle	extent () const =0
	Returns the extent of the layer. More...

virtual QString	fileRasterFilters () const
	Returns raster file filter string. More...

virtual QString	fileVectorFilters () const
	Returns vector file filter string. More...

virtual void	invalidateConnections (const QString &connection)
	Invalidate connections corresponding to specified name. More...

virtual bool	isValid () const =0
	Returns true if this is a valid layer. More...

virtual QgsLayerMetadata	layerMetadata () const
	Returns layer metadata collected from the provider's source. More...

virtual bool	leaveUpdateMode ()
	Leave update mode. More...

virtual QString	name () const =0
	Returns a provider name. More...

QVariant	providerProperty (ProviderProperty property, const QVariant &defaultValue=QVariant()) const
	Gets the current value of a certain provider property. More...

QVariant	providerProperty (int property, const QVariant &defaultValue) const
	Gets the current value of a certain provider property. More...

virtual void	reloadData ()
	Reloads the data from the source. More...

virtual bool	renderInPreview (const QgsDataProvider::PreviewContext &context)
	Returns whether the layer must be rendered in preview jobs. 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	setListening (bool isListening)
	Set whether the provider will listen to datasource notifications If set, the provider will issue notify signals. More...

void	setProviderProperty (ProviderProperty property, const QVariant &value)
	Allows setting arbitrary properties on the provider. More...

void	setProviderProperty (int property, const QVariant &value)
	Allows setting arbitrary properties on the provider. More...

virtual void	setSubLayerVisibility (const QString &name, bool vis)
	Set the visibility of the given sublayer name. More...

virtual bool	setSubsetString (const QString &subset, bool updateFeatureCount=true)
	Set the subset string used to create a subset of features in the layer. More...

void	setUri (const QgsDataSourceUri &uri)
	Set the data source specification. More...

virtual uint	subLayerCount () const
	Returns 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 () const
	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 () const
	Returns true if the 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...

QgsDataSourceUri	uri () const
	Gets the data source specification. More...

virtual bool	writeLayerMetadata (const QgsLayerMetadata &metadata)
	Writes layer metadata to the underlying provider source. More...

Static Public Attributes
static QString	SUBLAYER_SEPARATOR = QString( "!!::!!" )
	String sequence used for separating components of sublayers strings. More...

Protected Member Functions
void	appendError (const QgsErrorMessage &message)
	Add error message. More...

void	setError (const QgsError &error)
	Sets 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.

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 49 of file qgsdataprovider.h.

Member Enumeration Documentation

enum QgsDataProvider::DataCapability

Enumerator
NoDataCapabilities
File
Dir
Database
Net

Definition at line 76 of file qgsdataprovider.h.

enum QgsDataProvider::ProviderProperty

Properties are used to pass custom configuration options into data providers.

This enum defines a list of custom properties which can be used on different providers. It depends on the provider, which properties are supported. In addition to these default properties, providers can add their custom properties starting from CustomData.

Enumerator
EvaluateDefaultValues	Evaluate default values on provider side when calling QgsVectorDataProvider::defaultValue( int index ) rather than on commit.
CustomData	Custom properties for 3rd party providers or very provider-specific properties which are not expected to be of interest for other providers can be added starting from this value up.

Definition at line 93 of file qgsdataprovider.h.

Constructor & Destructor Documentation

QgsDataProvider::QgsDataProvider	(	const QString &	uri = `QString()`,
		const QgsDataProvider::ProviderOptions &	options = `QgsDataProvider::ProviderOptions()`
	)

inline

Create a new dataprovider with the specified in the uri.

Additional creation options are specified within the options value.

Definition at line 114 of file qgsdataprovider.h.

Member Function Documentation

void QgsDataProvider::appendError ( const QgsErrorMessage & message )

inlineprotected

Add error message.

Definition at line 573 of file qgsdataprovider.h.

virtual QgsCoordinateReferenceSystem QgsDataProvider::crs ( ) const

pure virtual

Returns the coordinate system for the data source.

If the provider isn't capable of returning its projection then an invalid QgsCoordinateReferenceSystem will be returned.

void QgsDataProvider::dataChanged ( )

signal

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

When emitted from a QgsVectorDataProvider, any cached information such as feature ids should be invalidated.

virtual QString QgsDataProvider::dataSourceUri ( bool expandAuthConfig = false ) const

inlinevirtual

Gets the data source specification.

This may be a path or database connection string

Parameters

expandAuthConfig Whether to expand any assigned authentication configuration

Returns: data source specification

Note: The default authentication configuration expansion is FALSE. This keeps credentials out of layer data source URIs and project files. Expansion should be specifically done only when needed within a provider

Definition at line 147 of file qgsdataprovider.h.

virtual QDateTime QgsDataProvider::dataTimestamp ( ) const

inlinevirtual

Current time stamp of data source.

Reimplemented in QgsRasterDataProvider.

Definition at line 381 of file qgsdataprovider.h.

virtual QString QgsDataProvider::description ( ) const

pure virtual

Returns description.

Returns 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 bool QgsDataProvider::enterUpdateMode ( )

inlinevirtual

Enter update mode.

This is aimed at providers that can open differently the connection to the datasource, according it to be in update mode or in read-only mode. A call to this method shall be balanced with a call to leaveUpdateMode(), if this method returns true.

Most providers will have an empty implementation for that method.

For backward compatibility, providers that implement enterUpdateMode() should still make sure to allow editing operations to work even if enterUpdateMode() is not explicitly called.

Several successive calls to enterUpdateMode() can be done. So there is a concept of stack of calls that must be handled by the provider. Only the first call to enterUpdateMode() will really turn update mode on.

Returns: true in case of success (or no-op implementation), false in case of failure.

Since: QGIS 2.16

Definition at line 418 of file qgsdataprovider.h.

virtual QgsError QgsDataProvider::error ( ) const

inlinevirtual

Gets 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 388 of file qgsdataprovider.h.

virtual QgsRectangle QgsDataProvider::extent ( ) const

pure virtual

Returns the extent of the layer.

Returns: QgsRectangle containing the extent of the layer

Implemented in QgsMeshDataProvider, and QgsRasterDataProvider.

virtual QString QgsDataProvider::fileRasterFilters ( ) const

inlinevirtual

Returns 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 366 of file qgsdataprovider.h.

virtual QString QgsDataProvider::fileVectorFilters ( ) const

inlinevirtual

Returns 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 350 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 void QgsDataProvider::invalidateConnections ( const QString & connection )

inlinevirtual

Invalidate connections corresponding to specified name.

Since: QGIS 2.16

Definition at line 394 of file qgsdataprovider.h.

virtual bool QgsDataProvider::isValid ( ) const

pure virtual

Returns true if this is a valid layer.

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

virtual QgsLayerMetadata QgsDataProvider::layerMetadata ( ) const

inlinevirtual

Returns layer metadata collected from the provider's source.

Individual data providers must implement this method if they support collecting metadata.

See also: writeLayerMetadata()

Since: QGIS 3.0

Definition at line 522 of file qgsdataprovider.h.

virtual bool QgsDataProvider::leaveUpdateMode ( )

inlinevirtual

Leave update mode.

This is aimed at providers that can open differently the connection to the datasource, according it to be in update mode or in read-only mode. This method shall be balanced with a successful call to enterUpdateMode().

Most providers will have an empty implementation for that method.

Several successive calls to enterUpdateMode() can be done. So there is a concept of stack of calls that must be handled by the provider. Only the last call to leaveUpdateMode() will really turn update mode off.

Returns: true in case of success (or no-op implementation), false in case of failure.

Since: QGIS 2.16

Definition at line 437 of file qgsdataprovider.h.

virtual QString QgsDataProvider::name ( ) const

pure virtual

Returns 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?

void QgsDataProvider::notify ( const QString & msg )

signal

Emitted when datasource issues a notification.

See also: setListening

Since: QGIS 3.0

QVariant QgsDataProvider::providerProperty	(	QgsDataProvider::ProviderProperty	property,
		const QVariant &	defaultValue = `QVariant()`
	)		const

Gets the current value of a certain provider property.

It depends on the provider which properties are supported.

Since: QGIS 2.16

Definition at line 30 of file qgsdataprovider.cpp.

QVariant QgsDataProvider::providerProperty	(	int	property,
		const QVariant &	defaultValue = `QVariant()`
	)		const

Gets the current value of a certain provider property.

It depends on the provider which properties are supported.

Since: QGIS 2.16

Definition at line 35 of file qgsdataprovider.cpp.

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 375 of file qgsdataprovider.h.

bool QgsDataProvider::renderInPreview ( const QgsDataProvider::PreviewContext & context )

virtual

Returns whether the layer must be rendered in preview jobs.

The context argument gives useful information which can be used to determine whether the layer should be rendered or not.

The base implementation returns true if lastRenderingTimeMs <= maxRenderingTimeMs.

Note: not available in Python bindings

Since: QGIS 3.0

Definition at line 45 of file qgsdataprovider.cpp.

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

Definition at line 133 of file qgsdataprovider.h.

void QgsDataProvider::setError ( const QgsError & error )

inlineprotected

Sets error message.

Definition at line 576 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 282 of file qgsdataprovider.h.

void QgsDataProvider::setListening ( bool isListening )

virtual

Set whether the provider will listen to datasource notifications If set, the provider will issue notify signals.

The default implementation does nothing.

See also: notify

Since: QGIS 3.0

Definition at line 40 of file qgsdataprovider.cpp.

void QgsDataProvider::setProviderProperty	(	QgsDataProvider::ProviderProperty	property,
		const QVariant &	value
	)

Allows setting arbitrary properties on the provider.

It depends on the provider which properties are supported.

Since: QGIS 2.16

Definition at line 20 of file qgsdataprovider.cpp.

void QgsDataProvider::setProviderProperty	(	int	property,
		const QVariant &	value
	)

Allows setting arbitrary properties on the provider.

It depends on the provider which properties are supported.

Since: QGIS 2.16

Definition at line 25 of file qgsdataprovider.cpp.

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

inlinevirtual

Set the visibility of the given sublayer name.

Definition at line 296 of file qgsdataprovider.h.

virtual bool QgsDataProvider::setSubsetString	(	const 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 209 of file qgsdataprovider.h.

void QgsDataProvider::setUri ( const QgsDataSourceUri & uri )

inline

Set the data source specification.

Since: QGIS 3.0

Definition at line 165 of file qgsdataprovider.h.

virtual uint QgsDataProvider::subLayerCount ( ) const

inlinevirtual

Returns the number of layers for the current data source.

Definition at line 271 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.

See also: SUBLAYER_SEPARATOR

Reimplemented in QgsRasterDataProvider.

Definition at line 243 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 262 of file qgsdataprovider.h.

virtual QString QgsDataProvider::subsetString ( ) const

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 229 of file qgsdataprovider.h.

virtual bool QgsDataProvider::supportsSubsetString ( ) const

inlinevirtual

Returns true if the provider supports setting of subset strings.

Definition at line 221 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 378 of file qgsdataprovider.h.

virtual void QgsDataProvider::updateExtents ( )

inlinevirtual

Update the extents of the layer.

Not implemented by default.

Definition at line 197 of file qgsdataprovider.h.

QgsDataSourceUri QgsDataProvider::uri ( ) const

inline

Gets the data source specification.

Since: QGIS 3.0

Definition at line 175 of file qgsdataprovider.h.

virtual bool QgsDataProvider::writeLayerMetadata ( const QgsLayerMetadata & metadata )

inlinevirtual

Writes layer metadata to the underlying provider source.

Support depends on individual provider capabilities.

Returns true if metadata was successfully written to the data provider.

See also: layerMetadata()

Since: QGIS 3.0

Definition at line 532 of file qgsdataprovider.h.

Member Data Documentation

QgsError QgsDataProvider::mError

protected

Error.

Definition at line 570 of file qgsdataprovider.h.

QDateTime QgsDataProvider::mTimestamp

protected

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

Definition at line 567 of file qgsdataprovider.h.

QString QgsDataProvider::SUBLAYER_SEPARATOR = QString( "!!::!!" )

static

String sequence used for separating components of sublayers strings.

See also: subLayers()

Since: QGIS 3.0

Definition at line 253 of file qgsdataprovider.h.

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

/build/qgis-3.4.15+24xenial/src/core/qgsdataprovider.h
/build/qgis-3.4.15+24xenial/src/core/qgsdataprovider.cpp

Classes

Public Types

Signals

Public Member Functions

Static Public Attributes

Protected Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation