QgsProcessingParameterExpression class

An expression parameter for processing algorithms.

Reference

Base classes

class QgsProcessingParameterDefinition: Base class for the definition of processing parameters.

Public static functions

static auto fromScriptCode(const QString& name, const QString& description, bool isOptional, const QString& definition) -> QgsProcessingParameterExpression*: Creates a new parameter using the definition from a script code.
static auto typeName() -> QString: Returns the type name for the parameter class.

Constructors, destructors, conversion operators

QgsProcessingParameterExpression(const QString& name, const QString& description = QString(), const QVariant& defaultValue = QVariant(), const QString& parentLayerParameterName = QString(), bool optional = false): Constructor for QgsProcessingParameterExpression.

Public functions

auto clone() const -> QgsProcessingParameterDefinition* override: Creates a clone of the parameter definition.
auto dependsOnOtherParameters() const -> QStringList override: Returns a list of other parameter names on which this parameter is dependent (e.g.
auto fromVariantMap(const QVariantMap& map) -> bool override: Restores this parameter to a QVariantMap.
auto parentLayerParameterName() const -> QString: Returns the name of the parent layer parameter, or an empty string if this is not set.
void setParentLayerParameterName(const QString& parentLayerParameterName): Sets the name of the parent layer parameter.
auto toVariantMap() const -> QVariantMap override: Saves this parameter to a QVariantMap.
auto type() const -> QString override: Unique parameter type name.
auto valueAsPythonString(const QVariant& value, QgsProcessingContext& context) const -> QString override: Returns a string version of the parameter input value, which is suitable for use as an input parameter value when running an algorithm directly from a Python command.

Function documentation

QStringList QgsProcessingParameterExpression::dependsOnOtherParameters() const override

Returns a list of other parameter names on which this parameter is dependent (e.g.

field parameters which depend on a parent layer parameter).

bool QgsProcessingParameterExpression::fromVariantMap(const QVariantMap& map) override

Restores this parameter to a QVariantMap.

Subclasses should ensure that they call the base class method.

QString QgsProcessingParameterExpression::parentLayerParameterName() const

Returns the name of the parent layer parameter, or an empty string if this is not set.

void QgsProcessingParameterExpression::setParentLayerParameterName(const QString& parentLayerParameterName)

Sets the name of the parent layer parameter.

Use an empty string if this is not required.

QVariantMap QgsProcessingParameterExpression::toVariantMap() const override

Saves this parameter to a QVariantMap.

Subclasses should ensure that they call the base class method and then extend the result with additional properties.

QString QgsProcessingParameterExpression::valueAsPythonString(const QVariant& value, QgsProcessingContext& context) const override

Returns a string version of the parameter input value, which is suitable for use as an input parameter value when running an algorithm directly from a Python command.

The returned value must be correctly escaped - e.g. string values must be wrapped in ' 's.