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

#include <qgsfield.h>

Public Member Functions
	QgsField (const QgsField &other)
Q_DECL_DEPRECATED	QgsField (const QString &name, QVariant::Type type, const QString &typeName=QString(), int len=0, int prec=0, const QString &comment=QString(), QVariant::Type subType=QVariant::Invalid)
	Constructor.
	QgsField (const QString &name=QString(), QMetaType::Type type=QMetaType::Type::UnknownType, const QString &typeName=QString(), int len=0, int prec=0, const QString &comment=QString(), QMetaType::Type subType=QMetaType::Type::UnknownType)
	Constructor.
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.
QString	comment () const
	Returns the field comment.
Qgis::FieldConfigurationFlags	configurationFlags () const
	Returns the Flags for the field (searchable, …).
const QgsFieldConstraints &	constraints () const
	Returns constraints which are present for the field.
bool	convertCompatible (QVariant &v, QString *errorMessage=nullptr) const
	Converts the provided variant to a compatible format.
QgsDefaultValue	defaultValueDefinition () const
	Returns the expression used when calculating the default value for the field.
QString	displayName () const
	Returns the name to use when displaying this field.
QString	displayNameWithAlias () const
	Returns the name to use when displaying this field and adds the alias in parenthesis if it is defined.
QString	displayString (const QVariant &v) const
	Formats string for display.
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.
Qgis::FieldDuplicatePolicy	duplicatePolicy () const
	Returns the field's duplicate policy, which indicates how field values should be handled during a duplicate operation.
QgsEditorWidgetSetup	editorWidgetSetup () const
	Gets the editor widget setup for the field.
QString	friendlyTypeString () const
	Returns a user friendly, translated representation of the field type.
bool	isDateOrTime () const
	Returns if this field is a date and/or time type.
bool	isNumeric () const
	Returns if this field is numeric.
bool	isReadOnly () const
	Returns `true` if this field is a read-only field.
int	length () const
	Gets the length of the field.
Qgis::FieldDomainMergePolicy	mergePolicy () const
	Returns the field's merge policy, which indicates how field values should be handled during a merge operation.
QMap< int, QVariant >	metadata () const
	Returns the map of field metadata.
QVariant	metadata (int property) const
	Returns a specific metadata property.
QVariant	metadata (Qgis::FieldMetadataProperty property) const
	Returns a specific metadata property.
QString	name () const
	Returns the name of the field.
	operator QVariant () const
	Allows direct construction of QVariants from fields.
bool	operator!= (const QgsField &other) const
QgsField &	operator= (const QgsField &other)
bool	operator== (const QgsField &other) const
int	precision () const
	Gets the precision of the field.
void	setAlias (const QString &alias)
	Sets the alias for the field (the friendly displayed name of the field ).
void	setComment (const QString &comment)
	Set the field comment.
void	setConfigurationFlags (Qgis::FieldConfigurationFlags flags)
	Sets the Flags for the field (searchable, …).
void	setConstraints (const QgsFieldConstraints &constraints)
	Sets constraints which are present for the field.
void	setDefaultValueDefinition (const QgsDefaultValue &defaultValueDefinition)
	Sets an expression to use when calculating the default value for the field.
void	setDuplicatePolicy (Qgis::FieldDuplicatePolicy policy)
	Sets the field's duplicate policy, which indicates how field values should be handled during a duplicate operation.
void	setEditorWidgetSetup (const QgsEditorWidgetSetup &v)
	Set the editor widget setup for the field.
void	setLength (int len)
	Set the field length.
void	setMergePolicy (Qgis::FieldDomainMergePolicy policy)
	Sets the field's merge policy, which indicates how field values should be handled during a merge operation.
void	setMetadata (const QMap< int, QVariant > metadata)
	Sets the map of field metadata.
void	setMetadata (int property, const QVariant &value)
	Sets a metadata property to value.
void	setMetadata (Qgis::FieldMetadataProperty property, const QVariant &value)
	Sets a metadata property to value.
void	setName (const QString &name)
	Set the field name.
void	setPrecision (int precision)
	Set the field precision.
void	setReadOnly (bool readOnly)
	Make field read-only if readOnly is set to true.
void	setSplitPolicy (Qgis::FieldDomainSplitPolicy policy)
	Sets the field's split policy, which indicates how field values should be handled during a split operation.
void	setSubType (QMetaType::Type subType)
	If the field is a collection, set its element's type.
Q_DECL_DEPRECATED void	setSubType (QVariant::Type subType)
	If the field is a collection, set its element's type.
void	setType (QMetaType::Type type)
	Set variant type.
Q_DECL_DEPRECATED void	setType (QVariant::Type type)
	Set variant type.
void	setTypeName (const QString &typeName)
	Set the field type.
Qgis::FieldDomainSplitPolicy	splitPolicy () const
	Returns the field's split policy, which indicates how field values should be handled during a split operation.
QMetaType::Type	subType () const
	If the field is a collection, gets its element's type.
QMetaType::Type	type () const
	Gets variant type of the field as it will be retrieved from data source.
QString	typeName () const
	Gets the field type.

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

Static Public Attributes
static constexpr int	MAX_WKT_LENGTH = 999

Properties
QString	alias
QString	comment
Qgis::FieldConfigurationFlags	configurationFlags
QgsFieldConstraints	constraints
QgsDefaultValue	defaultValueDefinition
bool	isDateOrTime
bool	isNumeric
bool	isReadOnly
int	length
QString	name
int	precision
QMetaType::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 53 of file qgsfield.h.

Constructor & Destructor Documentation

◆ QgsField() [1/3]

QgsField::QgsField	(	const QString &	name = QString(),
		QMetaType::Type	type = QMetaType::Type::UnknownType,
		const QString &	typeName = QString(),
		int	len = 0,
		int	prec = 0,
		const QString &	comment = QString(),
		QMetaType::Type	subType = QMetaType::Type::UnknownType )

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 50 of file qgsfield.cpp.

◆ QgsField() [2/3]

QgsField::QgsField	(	const QString &	name,
		QVariant::Type	type,
		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.

Deprecated: QGIS 3.38. Use the method with a QMetaType::Type argument instead.

Definition at line 56 of file qgsfield.cpp.

◆ QgsField() [3/3]

QgsField::QgsField ( const QgsField & other )

Definition at line 62 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()

Definition at line 293 of file qgsfield.cpp.

◆ comment()

QString QgsField::comment ( ) const

Returns the field comment.

Definition at line 178 of file qgsfield.cpp.

◆ configurationFlags()

Qgis::FieldConfigurationFlags QgsField::configurationFlags ( ) const

Returns the Flags for the field (searchable, …).

See also: setConfigurationFlags()

Since: QGIS 3.34

Definition at line 303 of file qgsfield.cpp.

◆ constraints()

const QgsFieldConstraints & QgsField::constraints ( ) const

Returns constraints which are present for the field.

See also: setConstraints()

Definition at line 288 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 475 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()

Definition at line 273 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()

Definition at line 97 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 105 of file qgsfield.cpp.

◆ displayString()

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

Formats string for display.

Definition at line 319 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 114 of file qgsfield.cpp.

◆ duplicatePolicy()

Qgis::FieldDuplicatePolicy QgsField::duplicatePolicy ( ) const

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

See also: setDuplicatePolicy()

Since: QGIS 3.38

Definition at line 772 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 747 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 141 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 218 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.

Definition at line 213 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 757 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 168 of file qgsfield.cpp.

◆ mergePolicy()

Qgis::FieldDomainMergePolicy QgsField::mergePolicy ( ) const

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

See also: setMergePolicy()

Since: QGIS 3.44

Definition at line 782 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 188 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 183 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 193 of file qgsfield.cpp.

◆ name()

QString QgsField::name ( ) const

Returns the name of the field.

See also: setName(); displayName()

Definition at line 92 of file qgsfield.cpp.

◆ operator QVariant()

QgsField::operator QVariant ( ) const

Allows direct construction of QVariants from fields.

Definition at line 737 of file qgsfield.cpp.

◆ operator!=()

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

Definition at line 87 of file qgsfield.cpp.

◆ operator=()

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

Definition at line 76 of file qgsfield.cpp.

◆ operator==()

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

Definition at line 82 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 173 of file qgsfield.cpp.

◆ readableConfigurationFlag()

QString QgsField::readableConfigurationFlag ( Qgis::FieldConfigurationFlag flag )

static

Returns the readable and translated value of the configuration flag.

Since: QGIS 3.16

Definition at line 453 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()

Definition at line 298 of file qgsfield.cpp.

◆ setComment()

void QgsField::setComment ( const QString & comment )

Set the field comment.

Definition at line 268 of file qgsfield.cpp.

◆ setConfigurationFlags()

void QgsField::setConfigurationFlags ( Qgis::FieldConfigurationFlags flags )

Sets the Flags for the field (searchable, …).

See also: configurationFlags()

Since: QGIS 3.34

Definition at line 308 of file qgsfield.cpp.

◆ setConstraints()

void QgsField::setConstraints ( const QgsFieldConstraints & constraints )

Sets constraints which are present for the field.

See also: constraints()

Definition at line 283 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()

Definition at line 278 of file qgsfield.cpp.

◆ setDuplicatePolicy()

void QgsField::setDuplicatePolicy ( Qgis::FieldDuplicatePolicy policy )

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

See also: duplicatePolicy()

Since: QGIS 3.38

Definition at line 777 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 742 of file qgsfield.cpp.

◆ setLength()

void QgsField::setLength ( int len )

Set the field length.

Parameters

len	Length of the field

Definition at line 259 of file qgsfield.cpp.

◆ setMergePolicy()

void QgsField::setMergePolicy ( Qgis::FieldDomainMergePolicy policy )

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

See also: mergePolicy()

Since: QGIS 3.44

Definition at line 787 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 198 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 208 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 203 of file qgsfield.cpp.

◆ setName()

void QgsField::setName ( const QString & name )

Set the field name.

Parameters

name	Name of the field

Definition at line 229 of file qgsfield.cpp.

◆ setPrecision()

void QgsField::setPrecision ( int precision )

Set the field precision.

Parameters

precision Precision of the field

Definition at line 263 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 752 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 767 of file qgsfield.cpp.

◆ setSubType() [1/2]

void QgsField::setSubType ( QMetaType::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.

Definition at line 244 of file qgsfield.cpp.

◆ setSubType() [2/2]

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.

Deprecated: QGIS 3.38. Use the method with a QMetaType::Type argument instead.

Definition at line 249 of file qgsfield.cpp.

◆ setType() [1/2]

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

Set variant type.

Definition at line 234 of file qgsfield.cpp.

◆ setType() [2/2]

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

Set variant type.

Deprecated: QGIS 3.38. Use the method with a QMetaType::Type argument instead.

Definition at line 239 of file qgsfield.cpp.

◆ setTypeName()

void QgsField::setTypeName ( const QString & typeName )

Set the field type.

Parameters

typeName Field type

Definition at line 254 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 762 of file qgsfield.cpp.

◆ subType()

QMetaType::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.

Definition at line 158 of file qgsfield.cpp.

◆ type()

QMetaType::Type QgsField::type ( ) const

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

Definition at line 153 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 163 of file qgsfield.cpp.

Member Data Documentation

◆ MAX_WKT_LENGTH

int QgsField::MAX_WKT_LENGTH = 999

staticconstexpr

Definition at line 578 of file qgsfield.h.

Property Documentation

◆ alias

QString QgsField::alias

readwrite

Definition at line 64 of file qgsfield.h.

◆ comment

QString QgsField::comment

readwrite

Definition at line 62 of file qgsfield.h.

◆ configurationFlags

Qgis::FieldConfigurationFlags QgsField::configurationFlags

readwrite

Definition at line 67 of file qgsfield.h.

◆ constraints

QgsFieldConstraints QgsField::constraints

readwrite

Definition at line 66 of file qgsfield.h.

◆ defaultValueDefinition

QgsDefaultValue QgsField::defaultValueDefinition

readwrite

Definition at line 65 of file qgsfield.h.

◆ isDateOrTime

bool QgsField::isDateOrTime

read

Definition at line 58 of file qgsfield.h.

◆ isNumeric

bool QgsField::isNumeric

read

Definition at line 57 of file qgsfield.h.

◆ isReadOnly

bool QgsField::isReadOnly

readwrite

Definition at line 68 of file qgsfield.h.

◆ length

int QgsField::length

readwrite

Definition at line 59 of file qgsfield.h.

◆ name

QString QgsField::name

readwrite

Definition at line 63 of file qgsfield.h.

◆ precision

int QgsField::precision

readwrite

Definition at line 60 of file qgsfield.h.

◆ type

QMetaType::Type QgsField::type

readwrite

Definition at line 61 of file qgsfield.h.

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

/build/qgis-3.99.0+git20251207+21b3aa880ba+99sid/src/core/qgsfield.h
/build/qgis-3.99.0+git20251207+21b3aa880ba+99sid/src/core/qgsfield.cpp

Public Member Functions

Static Public Member Functions

Static Public Attributes

Properties

Detailed Description

Constructor & Destructor Documentation

◆ QgsField() [1/3]

◆ QgsField() [2/3]

◆ QgsField() [3/3]

◆ ~QgsField()

Member Function Documentation

◆ alias()

◆ comment()

◆ configurationFlags()

◆ constraints()

◆ convertCompatible()

◆ defaultValueDefinition()

◆ displayName()

◆ displayNameWithAlias()

◆ displayString()

◆ displayType()

◆ duplicatePolicy()

◆ editorWidgetSetup()

◆ friendlyTypeString()

◆ isDateOrTime()

◆ isNumeric()

◆ isReadOnly()

◆ length()

◆ mergePolicy()

◆ metadata() [1/3]

◆ metadata() [2/3]

◆ metadata() [3/3]

◆ name()

◆ operator QVariant()

◆ operator!=()

◆ operator=()

◆ operator==()

◆ precision()

◆ readableConfigurationFlag()

◆ setAlias()

◆ setComment()

◆ setConfigurationFlags()

◆ setConstraints()

◆ setDefaultValueDefinition()

◆ setDuplicatePolicy()

◆ setEditorWidgetSetup()

◆ setLength()

◆ setMergePolicy()

◆ setMetadata() [1/3]

◆ setMetadata() [2/3]

◆ setMetadata() [3/3]

◆ setName()

◆ setPrecision()

◆ setReadOnly()

◆ setSplitPolicy()

◆ setSubType() [1/2]

◆ setSubType() [2/2]

◆ setType() [1/2]

◆ setType() [2/2]

◆ setTypeName()

◆ splitPolicy()

◆ subType()

◆ type()

◆ typeName()

Member Data Documentation

◆ MAX_WKT_LENGTH

Property Documentation

◆ alias

◆ comment

◆ configurationFlags

◆ constraints

◆ defaultValueDefinition

◆ isDateOrTime

◆ isNumeric

◆ isReadOnly

◆ length

◆ name

◆ precision

◆ type