QGIS/python/core/qgsdefaultvalue.sip

/************************************************************************
 * This file has been generated automatically from                      *
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 * src/core/qgsdefaultvalue.h                                           *
 *                                                                      *
 * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
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class QgsDefaultValue
{
%Docstring

 The QgsDefaultValue class provides a container for managing client
side default values for fields.

A QgsDefaultValue consists of an expression string that will be evaluated
on the client when a defeault field value needs to be generated.

Usual values for such an expression are

- `now()` for a timestamp for a record
- `@some_variable` to insert a project or application level variable like
the username of the one digitizing a feature
- `$length` to insert a derived attribute of a geometry

QgsDefaultValue also has a `applyOnUpdate` flag which will indicate that a
default value should also be applied when a feature is updated. If this is
not set, the default value will only be used when a feature is created.

.. versionadded:: 3.0
%End

%TypeHeaderCode
#include "qgsdefaultvalue.h"
%End
  public:

    QgsDefaultValue( const QString &expression = QString(), bool applyOnUpdate = false );
%Docstring
Create a new default value with the given ``expression`` and ``applyOnUpdate`` flag.

.. seealso:: :py:func:`QgsVectorLayer.setDefaultValueDefinition`
%End
    bool operator==( const QgsDefaultValue &other ) const;

    QString expression() const;
%Docstring
The expression will be evaluated whenever a default value needs
to be calculated for a field.
%End

    void setExpression( const QString &expression );
%Docstring
The expression will be evaluated whenever a default value needs
to be calculated for a field.
%End

    bool applyOnUpdate() const;
%Docstring
The applyOnUpdate flag determines if this expression should also be
applied when a feature is updated or only when it's created.
%End

    void setApplyOnUpdate( bool applyOnUpdate );
%Docstring
The applyOnUpdate flag determines if this expression should also be
applied when a feature is updated or only when it's created.
%End

    bool isValid() const;
%Docstring
Returns if this default value should be applied.

:return: false if the expression is a null string.
%End

    operator bool() const;

};

/************************************************************************
 * This file has been generated automatically from                      *
 *                                                                      *
 * src/core/qgsdefaultvalue.h                                           *
 *                                                                      *
 * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
 ************************************************************************/