Encapsulate a field in an attribute table or data source. More...

#include <qgsfield.h>

Public Types
enum class	ConfigurationFlag : int { None = 0 , NotSearchable = 1 << 1 , HideFromWms = 1 << 2 , HideFromWfs = 1 << 3 }
	Configuration flags for fields These flags are meant to be user-configurable and are not describing any information from the data provider. More...

Public Member Functions
	QgsField (const QgsField &other)
	Copy constructor. More...

	QgsField (const QString &name=QString(), QVariant::Type type=QVariant::Invalid, const QString &typeName=QString(), int len=0, int prec=0, const QString &comment=QString(), QVariant::Type subType=QVariant::Invalid)
	Constructor. More...

virtual	~QgsField ()

QString	alias () const
	Returns the alias for the field (the friendly displayed name of the field ), or an empty string if there is no alias. More...

QString	comment () const
	Returns the field comment. More...

QgsField::ConfigurationFlags	configurationFlags () const
	Returns the Flags for the field (searchable, …) More...

const QgsFieldConstraints &	constraints () const
	Returns constraints which are present for the field. More...

bool	convertCompatible (QVariant &v, QString *errorMessage=nullptr) const
	Converts the provided variant to a compatible format. More...

QgsDefaultValue	defaultValueDefinition () const
	Returns the expression used when calculating the default value for the field. More...

QString	displayName () const
	Returns the name to use when displaying this field. More...

QString	displayNameWithAlias () const
	Returns the name to use when displaying this field and adds the alias in parenthesis if it is defined. More...

QString	displayString (const QVariant &v) const
	Formats string for display. More...

QString	displayType (bool showConstraints=false) const
	Returns the type to use when displaying this field, including the length and precision of the datatype if applicable. More...

QgsEditorWidgetSetup	editorWidgetSetup () const
	Gets the editor widget setup for the field. More...

QString	friendlyTypeString () const
	Returns a user friendly, translated representation of the field type. More...

bool	isDateOrTime () const
	Returns if this field is a date and/or time type. More...

bool	isNumeric () const
	Returns if this field is numeric. More...

bool	isReadOnly () const
	Returns `true` if this field is a read-only field. More...

int	length () const
	Gets the length of the field. More...

QMap< int, QVariant >	metadata () const
	Returns the map of field metadata. More...

QVariant	metadata (int property) const
	Returns a specific metadata property. More...

QVariant	metadata (Qgis::FieldMetadataProperty property) const
	Returns a specific metadata property. More...

QString	name () const
	Returns the name of the field. More...

	operator QVariant () const
	Allows direct construction of QVariants from fields. More...

bool	operator!= (const QgsField &other) const

QgsField &	operator= (const QgsField &other)
	Assignment operator. More...

bool	operator== (const QgsField &other) const

int	precision () const
	Gets the precision of the field. More...

void	setAlias (const QString &alias)
	Sets the alias for the field (the friendly displayed name of the field ). More...

void	setComment (const QString &comment)
	Set the field comment. More...

void	setConfigurationFlags (QgsField::ConfigurationFlags configurationFlags)
	Sets the Flags for the field (searchable, …) More...

void	setConstraints (const QgsFieldConstraints &constraints)
	Sets constraints which are present for the field. More...

void	setDefaultValueDefinition (const QgsDefaultValue &defaultValueDefinition)
	Sets an expression to use when calculating the default value for the field. More...

void	setEditorWidgetSetup (const QgsEditorWidgetSetup &v)
	Set the editor widget setup for the field. More...

void	setLength (int len)
	Set the field length. More...

void	setMetadata (const QMap< int, QVariant > metadata)
	Sets the map of field metadata. More...

void	setMetadata (int property, const QVariant &value)
	Sets a metadata property to value. More...

void	setMetadata (Qgis::FieldMetadataProperty property, const QVariant &value)
	Sets a metadata property to value. More...

void	setName (const QString &name)
	Set the field name. More...

void	setPrecision (int precision)
	Set the field precision. More...

void	setReadOnly (bool readOnly)
	Make field read-only if readOnly is set to true. More...

void	setSplitPolicy (Qgis::FieldDomainSplitPolicy policy)
	Sets the field's split policy, which indicates how field values should be handled during a split operation. More...

void	setSubType (QVariant::Type subType)
	If the field is a collection, set its element's type. More...

void	setType (QVariant::Type type)
	Set variant type. More...

void	setTypeName (const QString &typeName)
	Set the field type. More...

Qgis::FieldDomainSplitPolicy	splitPolicy () const
	Returns the field's split policy, which indicates how field values should be handled during a split operation. More...

QVariant::Type	subType () const
	If the field is a collection, gets its element's type. More...

QVariant::Type	type () const
	Gets variant type of the field as it will be retrieved from data source. More...

QString	typeName () const
	Gets the field type. More...

Static Public Member Functions
static QString	readableConfigurationFlag (QgsField::ConfigurationFlag flag)
	Returns the readable and translated value of the configuration flag. More...

Static Public Attributes
static constexpr int	MAX_WKT_LENGTH = 999

Properties
QString	alias

QString	comment

ConfigurationFlags	configurationFlags

QgsFieldConstraints	constraints

QgsDefaultValue	defaultValueDefinition

bool	isDateOrTime

Q_GADGET bool	isNumeric

bool	isReadOnly

int	length

QString	name

int	precision

QVariant::Type	type

Detailed Description

Encapsulate a field in an attribute table or data source.

QgsField stores metadata about an attribute field, including name, type length, and if applicable, precision.

Note: QgsField objects are implicitly shared.

Definition at line 52 of file qgsfield.h.

Member Enumeration Documentation

◆ ConfigurationFlag

enum class QgsField::ConfigurationFlag : int

strong

Configuration flags for fields These flags are meant to be user-configurable and are not describing any information from the data provider.

Note: Flags are expressed in the negative forms so that default flags is None.

Since: QGIS 3.16

Enumerator
None	No flag is defined.
NotSearchable	Defines if the field is searchable (used in the locator search for instance)
HideFromWms	Field is not available if layer is served as WMS from QGIS server.
HideFromWfs	Field is not available if layer is served as WFS from QGIS server.

Definition at line 81 of file qgsfield.h.

Constructor & Destructor Documentation

◆ QgsField() [1/2]

QgsField::QgsField	(	const QString &	name = `QString()`,
		QVariant::Type	type = `QVariant::Invalid`,
		const QString &	typeName = `QString()`,
		int	len = `0`,
		int	prec = `0`,
		const QString &	comment = `QString()`,
		QVariant::Type	subType = `QVariant::Invalid`
	)

Constructor.

Constructs a new QgsField object.

Parameters

name	Field name
type	Field variant type, currently supported: String / Int / Double
typeName	Field type (e.g., char, varchar, text, int, serial, double). Field types are usually unique to the source and are stored exactly as returned from the data store.
len	Field length
prec	Field precision. Usually decimal places but may also be used in conjunction with other fields types (e.g., variable character fields)
comment	Comment for the field
subType	If the field is a collection, its element's type. When all the elements don't need to have the same type, leave this to QVariant::Invalid.

Definition at line 47 of file qgsfield.cpp.

◆ QgsField() [2/2]

QgsField::QgsField ( const QgsField & other )

Copy constructor.

Definition at line 53 of file qgsfield.cpp.

◆ ~QgsField()

QgsField::~QgsField ( )

virtualdefault

Member Function Documentation

◆ alias()

QString QgsField::alias ( ) const

Returns the alias for the field (the friendly displayed name of the field ), or an empty string if there is no alias.

See also: setAlias()

Since: QGIS 3.0

Definition at line 270 of file qgsfield.cpp.

◆ comment()

QString QgsField::comment ( ) const

Returns the field comment.

Definition at line 165 of file qgsfield.cpp.

◆ configurationFlags()

QgsField::ConfigurationFlags QgsField::configurationFlags ( ) const

Returns the Flags for the field (searchable, …)

Since: QGIS 3.16

Definition at line 280 of file qgsfield.cpp.

◆ constraints()

const QgsFieldConstraints & QgsField::constraints ( ) const

Returns constraints which are present for the field.

See also: setConstraints()

Since: QGIS 3.0

Definition at line 265 of file qgsfield.cpp.

◆ convertCompatible()

bool QgsField::convertCompatible	(	QVariant &	v,
		QString *	errorMessage = `nullptr`
	)		const

Converts the provided variant to a compatible format.

Parameters

v	The value to convert
errorMessage	if specified, will be set to a descriptive error when a conversion failure occurs

Returns: true if the conversion was successful

Definition at line 452 of file qgsfield.cpp.

◆ defaultValueDefinition()

QgsDefaultValue QgsField::defaultValueDefinition ( ) const

Returns the expression used when calculating the default value for the field.

Returns: expression evaluated when calculating default values for field, or an empty string if no default is set

See also: setDefaultValueDefinition()

Since: QGIS 3.0

Definition at line 250 of file qgsfield.cpp.

◆ displayName()

QString QgsField::displayName ( ) const

Returns the name to use when displaying this field.

This will be the field alias if set, otherwise the field name.

See also: name(); alias()

Since: QGIS 3.0

Definition at line 88 of file qgsfield.cpp.

◆ displayNameWithAlias()

QString QgsField::displayNameWithAlias ( ) const

Returns the name to use when displaying this field and adds the alias in parenthesis if it is defined.

This will be used when working close to the data structure (i.e. building expressions and queries), when the real field name must be shown but the alias is also useful to understand what the field represents.

See also: name(); alias()

Since: QGIS 3.12

Definition at line 96 of file qgsfield.cpp.

◆ displayString()

QString QgsField::displayString ( const QVariant & v ) const

Formats string for display.

Definition at line 296 of file qgsfield.cpp.

◆ displayType()

QString QgsField::displayType ( bool showConstraints = false ) const

Returns the type to use when displaying this field, including the length and precision of the datatype if applicable.

This will be used when the full datatype with details has to displayed to the user.

See also: type(); friendlyTypeString()

Since: QGIS 3.14

Definition at line 105 of file qgsfield.cpp.

◆ editorWidgetSetup()

QgsEditorWidgetSetup QgsField::editorWidgetSetup ( ) const

Gets the editor widget setup for the field.

Defaults may be set by the provider and can be overridden by manual field configuration.

Returns: the value

Definition at line 714 of file qgsfield.cpp.

◆ friendlyTypeString()

QString QgsField::friendlyTypeString ( ) const

Returns a user friendly, translated representation of the field type.

Unlike displayType(), this method only returns strings representing the field type and does not include length, precision or constraint information.

See also: type(); displayType()

Since: QGIS 3.14

Definition at line 128 of file qgsfield.cpp.

◆ isDateOrTime()

bool QgsField::isDateOrTime ( ) const

Returns if this field is a date and/or time type.

Since: QGIS 3.6

Definition at line 205 of file qgsfield.cpp.

◆ isNumeric()

bool QgsField::isNumeric ( ) const

Returns if this field is numeric.

Any integer or floating point type will return true for this.

Since: QGIS 2.18

Definition at line 200 of file qgsfield.cpp.

◆ isReadOnly()

bool QgsField::isReadOnly ( ) const

Returns true if this field is a read-only field.

This is the case for providers which support generated fields for instance.

Since: QGIS 3.18

Definition at line 724 of file qgsfield.cpp.

◆ length()

int QgsField::length ( ) const

Gets the length of the field.

Returns: int containing the length of the field

Definition at line 155 of file qgsfield.cpp.

◆ metadata() [1/3]

QMap< int, QVariant > QgsField::metadata ( ) const

Returns the map of field metadata.

Map keys should match values from the Qgis::FieldMetadataProperty enum.

See also: setMetadata()

Since: QGIS 3.32

Definition at line 175 of file qgsfield.cpp.

◆ metadata() [2/3]

QVariant QgsField::metadata ( int property ) const

Returns a specific metadata property.

See also: setMetadata()

Since: QGIS 3.32

Definition at line 170 of file qgsfield.cpp.

◆ metadata() [3/3]

QVariant QgsField::metadata ( Qgis::FieldMetadataProperty property ) const

Returns a specific metadata property.

See also: setMetadata()

Since: QGIS 3.32

Definition at line 180 of file qgsfield.cpp.

◆ name()

QString QgsField::name ( ) const

Returns the name of the field.

See also: setName(); displayName()

Definition at line 83 of file qgsfield.cpp.

◆ operator QVariant()

QgsField::operator QVariant ( ) const

inline

Allows direct construction of QVariants from fields.

Definition at line 474 of file qgsfield.h.

◆ operator!=()

bool QgsField::operator!= ( const QgsField & other ) const

Definition at line 78 of file qgsfield.cpp.

◆ operator=()

QgsField & QgsField::operator= ( const QgsField & other )

Assignment operator.

Definition at line 67 of file qgsfield.cpp.

◆ operator==()

bool QgsField::operator== ( const QgsField & other ) const

Definition at line 73 of file qgsfield.cpp.

◆ precision()

int QgsField::precision ( ) const

Gets the precision of the field.

Not all field types have a related precision.

Returns: int containing the precision or zero if not applicable to the field type.

Definition at line 160 of file qgsfield.cpp.

◆ readableConfigurationFlag()

QString QgsField::readableConfigurationFlag ( QgsField::ConfigurationFlag flag )

static

Returns the readable and translated value of the configuration flag.

Since: QGIS 3.16

Definition at line 430 of file qgsfield.cpp.

◆ setAlias()

void QgsField::setAlias ( const QString & alias )

Sets the alias for the field (the friendly displayed name of the field ).

Parameters

alias field alias, or empty string to remove an existing alias

See also: alias()

Since: QGIS 3.0

Definition at line 275 of file qgsfield.cpp.

◆ setComment()

void QgsField::setComment ( const QString & comment )

Set the field comment.

Definition at line 245 of file qgsfield.cpp.

◆ setConfigurationFlags()

void QgsField::setConfigurationFlags ( QgsField::ConfigurationFlags configurationFlags )

Sets the Flags for the field (searchable, …)

Since: QGIS 3.16

Definition at line 285 of file qgsfield.cpp.

◆ setConstraints()

void QgsField::setConstraints ( const QgsFieldConstraints & constraints )

Sets constraints which are present for the field.

See also: constraints()

Since: QGIS 3.0

Definition at line 260 of file qgsfield.cpp.

◆ setDefaultValueDefinition()

void QgsField::setDefaultValueDefinition ( const QgsDefaultValue & defaultValueDefinition )

Sets an expression to use when calculating the default value for the field.

Parameters

defaultValueDefinition expression to evaluate when calculating default values for field. Pass a default constructed QgsDefaultValue() to reset.

See also: defaultValueDefinition()

Since: QGIS 3.0

Definition at line 255 of file qgsfield.cpp.

◆ setEditorWidgetSetup()

void QgsField::setEditorWidgetSetup ( const QgsEditorWidgetSetup & v )

Set the editor widget setup for the field.

Parameters

v	The value to set

Definition at line 709 of file qgsfield.cpp.

◆ setLength()

void QgsField::setLength ( int len )

Set the field length.

Parameters

len	Length of the field

Definition at line 236 of file qgsfield.cpp.

◆ setMetadata() [1/3]

void QgsField::setMetadata ( const QMap< int, QVariant > metadata )

Sets the map of field metadata.

Map keys should match values from the Qgis::FieldMetadataProperty enum.

See also: metadata()

Since: QGIS 3.32

Definition at line 185 of file qgsfield.cpp.

◆ setMetadata() [2/3]

void QgsField::setMetadata	(	int	property,
		const QVariant &	value
	)

Sets a metadata property to value.

See also: metadata()

Since: QGIS 3.32

Definition at line 195 of file qgsfield.cpp.

◆ setMetadata() [3/3]

void QgsField::setMetadata	(	Qgis::FieldMetadataProperty	property,
		const QVariant &	value
	)

Sets a metadata property to value.

See also: metadata()

Since: QGIS 3.32

Definition at line 190 of file qgsfield.cpp.

◆ setName()

void QgsField::setName ( const QString & name )

Set the field name.

Parameters

name	Name of the field

Definition at line 216 of file qgsfield.cpp.

◆ setPrecision()

void QgsField::setPrecision ( int precision )

Set the field precision.

Parameters

precision Precision of the field

Definition at line 240 of file qgsfield.cpp.

◆ setReadOnly()

void QgsField::setReadOnly ( bool readOnly )

Make field read-only if readOnly is set to true.

This is the case for providers which support generated fields for instance.

Since: QGIS 3.18

Definition at line 719 of file qgsfield.cpp.

◆ setSplitPolicy()

void QgsField::setSplitPolicy ( Qgis::FieldDomainSplitPolicy policy )

Sets the field's split policy, which indicates how field values should be handled during a split operation.

See also: splitPolicy()

Since: QGIS 3.30

Definition at line 734 of file qgsfield.cpp.

◆ setSubType()

void QgsField::setSubType ( QVariant::Type subType )

If the field is a collection, set its element's type.

When all the elements don't need to have the same type, set this to QVariant::Invalid.

Since: QGIS 3.0

Definition at line 226 of file qgsfield.cpp.

◆ setType()

void QgsField::setType ( QVariant::Type type )

Set variant type.

Definition at line 221 of file qgsfield.cpp.

◆ setTypeName()

void QgsField::setTypeName ( const QString & typeName )

Set the field type.

Parameters

typeName Field type

Definition at line 231 of file qgsfield.cpp.

◆ splitPolicy()

Qgis::FieldDomainSplitPolicy QgsField::splitPolicy ( ) const

Returns the field's split policy, which indicates how field values should be handled during a split operation.

See also: setSplitPolicy()

Since: QGIS 3.30

Definition at line 729 of file qgsfield.cpp.

◆ subType()

QVariant::Type QgsField::subType ( ) const

If the field is a collection, gets its element's type.

When all the elements don't need to have the same type, this returns QVariant::Invalid.

Since: QGIS 3.0

Definition at line 145 of file qgsfield.cpp.

◆ type()

QVariant::Type QgsField::type ( ) const

Gets variant type of the field as it will be retrieved from data source.

Definition at line 140 of file qgsfield.cpp.

◆ typeName()

QString QgsField::typeName ( ) const

Gets the field type.

Field types vary depending on the data source. Examples are char, int, double, blob, geometry, etc. The type is stored exactly as the data store reports it, with no attempt to standardize the value.

Returns: QString containing the field type

Definition at line 150 of file qgsfield.cpp.

Member Data Documentation

◆ MAX_WKT_LENGTH

constexpr int QgsField::MAX_WKT_LENGTH = 999

staticconstexpr

Definition at line 539 of file qgsfield.h.