QgsField class

Encapsulate a field in an attribute table or data source.

Reference
- Constructors, destructors, conversion operators
- Public functions

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

Constructors, destructors, conversion operators

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.
QgsField(const QgsField& other): Copy constructor.
operator QVariant() const: Allows direct construction of QVariants from fields.

Public functions

auto alias() const -> QString: Returns the alias for the field (the friendly displayed name of the field ), or an empty string if there is no alias.
auto comment() const -> QString: Returns the field comment.
auto constraints() const -> const QgsFieldConstraints&: Returns constraints which are present for the field.
auto convertCompatible(QVariant& v) const -> bool: Converts the provided variant to a compatible format.
auto defaultValueDefinition() const -> QgsDefaultValue: Returns the expression used when calculating the default value for the field.
auto displayName() const -> QString: Returns the name to use when displaying this field.
auto displayString(const QVariant& v) const -> QString: Formats string for display.
auto editorWidgetSetup() const -> QgsEditorWidgetSetup: Gets the editor widget setup for the field.
auto isNumeric() const -> bool: Returns if this field is numeric.
auto length() const -> int: Gets the length of the field.
auto name() const -> QString: Returns the name of the field.
auto operator=(const QgsField& other) -> QgsField&: Assignment operator.
auto precision() const -> int: 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 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 setEditorWidgetSetup(const QgsEditorWidgetSetup& v): Set the editor widget setup for the field.
void setLength(int len): Set the field length.
void setName(const QString& name): Set the field name.
void setPrecision(int precision): Set the field precision.
void setSubType(QVariant::Type subType): If the field is a collection, set its element's type.
void setType(QVariant::Type type): Set variant type.
void setTypeName(const QString& typeName): Set the field type.
auto subType() const -> QVariant::Type: If the field is a collection, gets its element's type.
auto type() const -> QVariant::Type: Gets variant type of the field as it will be retrieved from data source.
auto typeName() const -> QString: Gets the field type.

Function documentation

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.

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.

Constructs a new QgsField object.

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.

const QgsFieldConstraints& QgsField::constraints() const

Returns constraints which are present for the field.

bool QgsField::convertCompatible(QVariant& v) const

Converts the provided variant to a compatible format.

Parameters
v	The value to convert
Returns	True if the conversion was successful

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

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.

QgsEditorWidgetSetup QgsField::editorWidgetSetup() const

Gets the editor widget setup for the field.

Returns	the value

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

bool QgsField::isNumeric() const

Returns if this field is numeric.

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

int QgsField::length() const

Gets the length of the field.

Returns	int containing the length of the field

QString QgsField::name() const

Returns the name of the field.

int QgsField::precision() const

Gets the precision of the field.

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

Not all field types have a related precision.

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

void QgsField::setConstraints(const QgsFieldConstraints& constraints)

Sets constraints which are present for the field.

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.

void QgsField::setEditorWidgetSetup(const QgsEditorWidgetSetup& v)

Set the editor widget setup for the field.

Parameters
v	The value to set

void QgsField::setLength(int len)

Set the field length.

Parameters
len	Length of the field

void QgsField::setName(const QString& name)

Set the field name.

Parameters
name	Name of the field

void QgsField::setPrecision(int precision)

Set the field precision.

Parameters
precision	Precision of the field

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.

void QgsField::setTypeName(const QString& typeName)

Set the field type.

Parameters
typeName	Field type

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.

QString QgsField::typeName() const

Gets the field type.

Returns	QString containing 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.