QGIS API Documentation  3.3.0-Master (4010e79)
Public Member Functions | Properties | List of all members
QgsField Class Reference

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

#include <qgsfield.h>

Public Member Functions

 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...
 
 QgsField (const QgsField &other)
 Copy constructor. More...
 
virtual ~QgsField ()=default
 
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...
 
const QgsFieldConstraintsconstraints () const
 Returns constraints which are present for the field. More...
 
bool convertCompatible (QVariant &v) 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 displayString (const QVariant &v) const
 Formats string for display. More...
 
QgsEditorWidgetSetup editorWidgetSetup () const
 Gets the editor widget setup for the field. More...
 
bool isNumeric () const
 Returns if this field is numeric. More...
 
int length () const
 Gets the length of the field. 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
 
QgsFieldoperator= (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 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 setName (const QString &name)
 Set the field name. More...
 
void setPrecision (int precision)
 Set the field precision. 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...
 
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...
 

Properties

QString alias
 
QString comment
 
QgsFieldConstraints constraints
 
QgsDefaultValue defaultValueDefinition
 
bool isNumeric
 
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 48 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
nameField name
typeField variant type, currently supported: String / Int / Double
typeNameField 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.
lenField length
precField precision. Usually decimal places but may also be used in conjunction with other fields types (e.g., variable character fields)
commentComment for the field
subTypeIf 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 54 of file qgsfield.cpp.

◆ ~QgsField()

virtual 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

◆ comment()

QString QgsField::comment ( ) const

Returns the field comment.

◆ constraints()

const QgsFieldConstraints& QgsField::constraints ( ) const

Returns constraints which are present for the field.

See also
setConstraints()
Since
QGIS 3.0

◆ convertCompatible()

bool QgsField::convertCompatible ( QVariant &  v) const

Converts the provided variant to a compatible format.

Parameters
vThe value to convert
Returns
True if the conversion was successful

Definition at line 272 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

◆ 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 87 of file qgsfield.cpp.

◆ displayString()

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

Formats string for display.

Definition at line 206 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 401 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

◆ length()

int QgsField::length ( ) const

Gets the length of the field.

Returns
int containing the length of the field

◆ name()

QString QgsField::name ( ) const

Returns the name of the field.

See also
setName()
displayName()

◆ operator QVariant()

QgsField::operator QVariant ( ) const
inline

Allows direct construction of QVariants from fields.

Definition at line 316 of file qgsfield.h.

◆ operator!=()

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

Definition at line 77 of file qgsfield.cpp.

◆ operator=()

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

Assignment operator.

Definition at line 66 of file qgsfield.cpp.

◆ operator==()

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

Definition at line 72 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.

◆ setAlias()

void QgsField::setAlias ( const QString &  alias)

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

Parameters
aliasfield alias, or empty string to remove an existing alias
See also
alias()
Since
QGIS 3.0

Definition at line 195 of file qgsfield.cpp.

◆ setComment()

void QgsField::setComment ( const QString &  comment)

Set the field comment.

Definition at line 165 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 180 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
defaultValueDefinitionexpression 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 175 of file qgsfield.cpp.

◆ setEditorWidgetSetup()

void QgsField::setEditorWidgetSetup ( const QgsEditorWidgetSetup v)

Set the editor widget setup for the field.

Parameters
vThe value to set

Definition at line 396 of file qgsfield.cpp.

◆ setLength()

void QgsField::setLength ( int  len)

Set the field length.

Parameters
lenLength of the field

Definition at line 156 of file qgsfield.cpp.

◆ setName()

void QgsField::setName ( const QString &  name)

Set the field name.

Parameters
nameName of the field

Definition at line 136 of file qgsfield.cpp.

◆ setPrecision()

void QgsField::setPrecision ( int  precision)

Set the field precision.

Parameters
precisionPrecision of the field

Definition at line 160 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 146 of file qgsfield.cpp.

◆ setType()

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

Set variant type.

Definition at line 141 of file qgsfield.cpp.

◆ setTypeName()

void QgsField::setTypeName ( const QString &  typeName)

Set the field type.

Parameters
typeNameField type

Definition at line 151 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 100 of file qgsfield.cpp.

◆ type()

QVariant::Type QgsField::type ( ) const

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

◆ 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 105 of file qgsfield.cpp.

Property Documentation

◆ alias

QString QgsField::alias
readwrite

Definition at line 58 of file qgsfield.h.

◆ comment

QString QgsField::comment
readwrite

Definition at line 56 of file qgsfield.h.

◆ constraints

const QgsFieldConstraints & QgsField::constraints
readwrite

Definition at line 60 of file qgsfield.h.

◆ defaultValueDefinition

QgsDefaultValue QgsField::defaultValueDefinition
readwrite

Definition at line 59 of file qgsfield.h.

◆ isNumeric

bool QgsField::isNumeric
read

Definition at line 52 of file qgsfield.h.

◆ length

int QgsField::length
readwrite

Definition at line 53 of file qgsfield.h.

◆ name

QString QgsField::name
readwrite

Definition at line 57 of file qgsfield.h.

◆ precision

int QgsField::precision
readwrite

Definition at line 54 of file qgsfield.h.

◆ type

QVariant::Type QgsField::type
readwrite

Definition at line 55 of file qgsfield.h.


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