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







class QgsExpression
{
%Docstring(signature="appended")
Class for parsing and evaluation of expressions (formerly called "search
strings"). The expressions try to follow both syntax and semantics of
SQL expressions.

Usage:

.. code-block:: python

       exp = QgsExpression("gid*2 > 10 and type not in ('D','F')")
       if exp.hasParserError():
           # show error message with parserErrorString() and exit

       result = exp.evaluate(feature, fields)
       if exp.hasEvalError():
           # show error message with evalErrorString()
       else:
           # examine the result

Three Value Logic
-----------------

Similarly to SQL, this class supports three-value logic:
true/false/unknown. Unknown value may be a result of operations with
missing data (NULL). Please note that NULL is different value than zero
or an empty string. For example 3 > NULL returns unknown.

There is no special (three-value) 'boolean' type: true/false is
represented as 1/0 integer, unknown value is represented the same way as
NULL values: NULL QVariant.

Performance
-----------

For better performance with many evaluations you may first call
prepare(fields) function to find out indices of columns and then
repeatedly call evaluate(feature).

Type conversion
---------------

Operators and functions that expect arguments to be of a particular type
automatically convert the arguments to that type, e.g. sin('2.1') will
convert the argument to a double, length(123) will first convert the
number to a string. Explicit conversion can be achieved with to_int,
to_real, to_string functions. If implicit or explicit conversion is
invalid, the evaluation returns an error. Comparison operators do
numeric comparison in case both operators are numeric (int/double) or
they can be converted to numeric types.

Implicit sharing
----------------

This class is implicitly shared, copying has a very low overhead. It is
normally preferable to call `QgsExpression( otherExpression )` instead
of `QgsExpression( otherExpression.expression() )`. A deep copy will
only be made when :py:func:`~prepare` is called. For usage this means
mainly, that you should normally keep an unprepared master copy of a
:py:class:`QgsExpression` and whenever using it with a particular
:py:class:`QgsFeatureIterator` copy it just before and prepare it using
the same context as the iterator.

Implicit sharing was added in 2.14
%End

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

    struct ParserError
    {
      enum ParserErrorType /BaseType=IntEnum/
      {
        Unknown,
        FunctionUnknown,
        FunctionWrongArgs,
        FunctionInvalidParams,
        FunctionNamedArgsError
      };

      ParserErrorType errorType;

      QString errorMsg;

      int firstLine;

      int firstColumn;

      int lastLine;

      int lastColumn;
    };

    QgsExpression( const QString &expr );
%Docstring
Creates a new expression based on the provided string. The string will
immediately be parsed. For optimization
:py:func:`~QgsExpression.prepare` should always be called before every
loop in which this expression is used.
%End

    QgsExpression( const QgsExpression &other );
%Docstring
Create a copy of this expression. This is preferred over recreating an
expression from a string since it does not need to be re-parsed.
%End



    QgsExpression();
%Docstring
Create an empty expression.
%End

    ~QgsExpression();

    bool operator==( const QgsExpression &other ) const;

    bool isValid() const;
%Docstring
Checks if this expression is valid. A valid expression could be parsed
but does not necessarily evaluate properly.
%End

    bool hasParserError() const;
%Docstring
Returns ``True`` if an error occurred when parsing the input expression
%End
    QString parserErrorString() const;
%Docstring
Returns parser error
%End

    QList<QgsExpression::ParserError> parserErrors() const;
%Docstring
Returns parser error details including location of error.
%End

    const QgsExpressionNode *rootNode() const;
%Docstring
Returns the root node of the expression.

The root node is ``None`` if parsing has failed.
%End

    bool prepare( const QgsExpressionContext *context );
%Docstring
Gets the expression ready for evaluation - find out column indexes.

:param context: context for preparing expression
%End

    QSet<QString> referencedColumns() const;
%Docstring
Gets list of columns referenced by the expression.

.. note::

   If the returned list contains the :py:class:`QgsFeatureRequest`.AllAttributes constant then
   all attributes from the layer are required for evaluation of the expression.
   :py:class:`QgsFeatureRequest`.setSubsetOfAttributes automatically handles this case.

.. warning::

   If the expression has been prepared via a call to :py:func:`QgsExpression.prepare()`,
   or a call to :py:func:`QgsExpressionNode.prepare()` for a node has been made, then parts of
   the expression may have been determined to evaluate to a static pre-calculatable value.
   In this case the results will omit attribute indices which are used by these
   pre-calculated nodes, regardless of their actual referenced columns.
   If you are seeking to use these functions to introspect an expression you must
   take care to do this with an unprepared expression.

.. seealso:: :py:func:`referencedAttributeIndexes`
%End

    QSet<QString> referencedVariables() const;
%Docstring
Returns a list of all variables which are used in this expression. If
the list contains a NULL QString, there is a variable name used which is
determined at runtime.

.. note::

   In contrast to the :py:func:`~QgsExpression.referencedColumns` function this method
   is not affected by any previous calls to :py:func:`QgsExpression.prepare()`,
   or :py:func:`QgsExpressionNode.prepare()`.
%End

    QSet<QString> referencedFunctions() const;
%Docstring
Returns a list of the names of all functions which are used in this
expression.

.. note::

   In contrast to the :py:func:`~QgsExpression.referencedColumns` function this method
   is not affected by any previous calls to :py:func:`QgsExpression.prepare()`,
   or :py:func:`QgsExpressionNode.prepare()`.

.. versionadded:: 3.2
%End


    QSet<int> referencedAttributeIndexes( const QgsFields &fields ) const;
%Docstring
Returns a list of field name indexes obtained from the provided fields.

.. warning::

   If the expression has been prepared via a call to :py:func:`QgsExpression.prepare()`,
   or a call to :py:func:`QgsExpressionNode.prepare()` for a node has been made, then parts of
   the expression may have been determined to evaluate to a static pre-calculatable value.
   In this case the results will omit attribute indices which are used by these
   pre-calculated nodes, regardless of their actual referenced columns.
   If you are seeking to use these functions to introspect an expression you must
   take care to do this with an unprepared expression.
%End

    bool needsGeometry() const;
%Docstring
Returns ``True`` if the expression uses feature geometry for some
computation
%End


    QVariant evaluate();
%Docstring
Evaluate the feature and return the result.

.. note::

   this method does not expect that :py:func:`~QgsExpression.prepare` has been called on this instance
%End

    QVariant evaluate( const QgsExpressionContext *context );
%Docstring
Evaluate the expression against the specified context and return the
result.

:param context: context for evaluating expression

.. note::

   :py:func:`~QgsExpression.prepare` should be called before calling this method.
%End

    bool hasEvalError() const;
%Docstring
Returns ``True`` if an error occurred when evaluating last input
%End
    QString evalErrorString() const;
%Docstring
Returns evaluation error
%End
    void setEvalErrorString( const QString &str );
%Docstring
Sets evaluation error (used internally by evaluation functions)
%End

    bool isField() const;
%Docstring
Checks whether an expression consists only of a single field reference

.. seealso:: :py:func:`expressionToLayerFieldIndex`
%End

    static int expressionToLayerFieldIndex( const QString &expression, const QgsVectorLayer *layer );
%Docstring
Attempts to resolve an expression to a field index from the given
``layer``.

Given a string which may either directly match a field name from a
layer, OR may be an expression which consists only of a single field
reference for that layer, this method will return the corresponding
field index.

:return: field index if found, or -1 if ``expression`` does not
         represent a field from the layer.

.. seealso:: :py:func:`isField`

.. versionadded:: 3.22
%End

    static QString quoteFieldExpression( const QString &expression, const QgsVectorLayer *layer );
%Docstring
Validate if the expression is a field in the ``layer`` and ensure it is
quoted.

Given a string which may either directly match a field name from a
layer, OR may be an expression which consists only of a single field
reference for that layer, this method will return the quoted field.

:return: the ``expression`` if not a field or quotes are not required,
         otherwise returns a quoted field.

.. seealso:: :py:func:`expressionToLayerFieldIndex`

.. versionadded:: 3.24
%End

    static bool checkExpression( const QString &text, const QgsExpressionContext *context, QString &errorMessage /Out/ );
%Docstring
Tests whether a string is a valid expression.

:param text: string to test
:param context: optional expression context

:return: - ``True`` if string is a valid expression
         - errorMessage: will be filled with any error message from the
           validation
%End

    void setExpression( const QString &expression );
%Docstring
Set the expression string, will reset the whole internal structure.
%End

    QString expression() const;
%Docstring
Returns the original, unmodified expression string. If there was none
supplied because it was constructed by sole API calls,
:py:func:`~QgsExpression.dump` will be used to create one instead.
%End

    QString dump() const;
%Docstring
Returns an expression string, constructed from the internal abstract
syntax tree. This does not contain any nice whitespace formatting or
comments. In general it is preferable to use
:py:func:`~QgsExpression.expression` instead.
%End

    QgsDistanceArea *geomCalculator();
%Docstring
Returns calculator used for distance and area calculations (used by
$length, $area and $perimeter functions only)

.. seealso:: :py:func:`setGeomCalculator`

.. seealso:: :py:func:`distanceUnits`

.. seealso:: :py:func:`areaUnits`
%End

    void setGeomCalculator( const QgsDistanceArea *calc );
%Docstring
Sets the geometry calculator used for distance and area calculations in
expressions. (used by $length, $area and $perimeter functions only). If
the geometry calculator is set to ``None`` (default),
:py:func:`~QgsExpression.prepare` will read variables from the
expression context ("project_ellipsoid", "_project_transform_context"
and "_layer_crs") to build a geometry calculator. If these variables
does not exist and if :py:func:`~QgsExpression.setGeomCalculator` is not
called, all distance and area calculations are performed using simple
Cartesian methods (ie no ellipsoidal calculations).

:param calc: geometry calculator. Ownership is not transferred. Set to
             ``None`` to force Cartesian calculations.

.. seealso:: :py:func:`geomCalculator`
%End

    Qgis::DistanceUnit distanceUnits() const;
%Docstring
Returns the desired distance units for calculations involving
:py:func:`~QgsExpression.geomCalculator`, e.g., "$length" and
"$perimeter".

.. note::

   distances are only converted when a :py:func:`~QgsExpression.geomCalculator` has been set

.. seealso:: :py:func:`setDistanceUnits`

.. seealso:: :py:func:`areaUnits`
%End

    void setDistanceUnits( Qgis::DistanceUnit unit );
%Docstring
Sets the desired distance units for calculations involving
:py:func:`~QgsExpression.geomCalculator`, e.g., "$length" and
"$perimeter". If distance units are set to
:py:class:`QgsUnitTypes`.DistanceUnknownUnit (default),
:py:func:`~QgsExpression.prepare` will read variables from the
expression context ("project_distance_units") to determine distance
units.

.. note::

   distances are only converted when a :py:func:`~QgsExpression.geomCalculator` has been set

.. seealso:: :py:func:`distanceUnits`

.. seealso:: :py:func:`setAreaUnits`
%End

    Qgis::AreaUnit areaUnits() const;
%Docstring
Returns the desired areal units for calculations involving
:py:func:`~QgsExpression.geomCalculator`, e.g., "$area".

.. note::

   areas are only converted when a :py:func:`~QgsExpression.geomCalculator` has been set

.. seealso:: :py:func:`setAreaUnits`

.. seealso:: :py:func:`distanceUnits`
%End

    void setAreaUnits( Qgis::AreaUnit unit );
%Docstring
Sets the desired areal units for calculations involving
:py:func:`~QgsExpression.geomCalculator`, e.g., "$area". If distance
units are set to :py:class:`QgsUnitTypes`.AreaUnknownUnit (default),
:py:func:`~QgsExpression.prepare` will read variables from the
expression context ("project_distance_units") to determine distance
units.

.. note::

   areas are only converted when a :py:func:`~QgsExpression.geomCalculator` has been set

.. seealso:: :py:func:`areaUnits`

.. seealso:: :py:func:`setDistanceUnits`
%End

    static QString replaceExpressionText( const QString &action, const QgsExpressionContext *context,
                                          const QgsDistanceArea *distanceArea = 0 );
%Docstring
This function replaces each expression between [% and %] in the string
with the result of its evaluation with the specified context

Additional substitutions can be passed through the substitutionMap
parameter

:param action: The source string in which placeholders should be
               replaced.
:param context: Expression context
:param distanceArea: Optional :py:class:`QgsDistanceArea`. If specified,
                     the :py:class:`QgsDistanceArea` is used for
                     distance and area conversion
%End

    static QSet<QString> referencedVariables( const QString &text );
%Docstring
This function returns variables in each expression between [% and %].

:param text: The source string in which variables should be searched.

.. versionadded:: 3.2
%End

    static double evaluateToDouble( const QString &text, double fallbackValue );
%Docstring
Attempts to evaluate a text string as an expression to a resultant
double value.

:param text: text to evaluate as expression
:param fallbackValue: value to return if text can not be evaluated as a
                      double

:return: evaluated double value, or fallback value

.. note::

   this method is inefficient for bulk evaluation of expressions, it is intended
   for one-off evaluations only.
%End

    enum SpatialOperator /BaseType=IntEnum/
    {
      soBbox,
      soIntersects,
      soContains,
      soCrosses,
      soEquals,
      soDisjoint,
      soOverlaps,
      soTouches,
      soWithin,
    };

    static const QList<QgsExpressionFunction *> &Functions();

    static const QStringList &BuiltinFunctions();

    static bool registerFunction( QgsExpressionFunction *function, bool transferOwnership = false );
%Docstring
Registers a function to the expression engine. This is required to allow
expressions to utilize the function.

:param function: function to register
:param transferOwnership: set to ``True`` to transfer ownership of
                          function to expression engine

:return: ``True`` on successful registration

.. seealso:: :py:func:`unregisterFunction`
%End

    static bool unregisterFunction( const QString &name );
%Docstring
Unregisters a function from the expression engine. The function will no
longer be usable in expressions.

:param name: function name

.. seealso:: :py:func:`registerFunction`
%End

    static void cleanRegisteredFunctions();
%Docstring
Deletes all registered functions whose ownership have been transferred
to the expression engine.
%End

    static bool isFunctionName( const QString &name );
%Docstring
tells whether the identifier is a name of existing function
%End

    static int functionIndex( const QString &name );
%Docstring
Returns index of the function in Functions array
%End

    static int functionCount();
%Docstring
Returns the number of functions defined in the parser

:return: The number of function defined in the parser.
%End

    static QString quotedColumnRef( QString name );
%Docstring
Returns a quoted column reference (in double quotes)

.. seealso:: :py:func:`quotedString`

.. seealso:: :py:func:`quotedValue`
%End

    static QString quotedString( QString text );
%Docstring
Returns a quoted version of a string (in single quotes)

.. seealso:: :py:func:`quotedValue`

.. seealso:: :py:func:`quotedColumnRef`
%End

    static QString quotedValue( const QVariant &value );
%Docstring
Returns a string representation of a literal value, including
appropriate quotations where required.

:param value: value to convert to a string representation

.. seealso:: :py:func:`quotedString`

.. seealso:: :py:func:`quotedColumnRef`
%End

    static QString quotedValue( const QVariant &value, QMetaType::Type type );
%Docstring
Returns a string representation of a literal value, including
appropriate quotations where required.

:param value: value to convert to a string representation
:param type: value type

.. seealso:: :py:func:`quotedString`

.. seealso:: :py:func:`quotedColumnRef`
%End

 static QString quotedValue( const QVariant &value, QVariant::Type type ) /Deprecated/;
%Docstring
Returns a string representation of a literal value, including
appropriate quotations where required.

:param value: value to convert to a string representation
:param type: value type

.. seealso:: :py:func:`quotedString`

.. seealso:: :py:func:`quotedColumnRef`

.. deprecated:: 3.38

   Use the method with a QMetaType.Type argument instead.
%End



    static QString helpText( QString name );
%Docstring
Returns the help text for a specified function.

:param name: function name

.. seealso:: :py:func:`variableHelpText`

.. seealso:: :py:func:`formatVariableHelp`
%End

    static QStringList tags( const QString &name );
%Docstring
Returns a string list of search tags for a specified function.

:param name: function name

.. versionadded:: 3.12
%End

    static bool addVariableHelpText( const QString name, const QString &description );
%Docstring
Adds a help string for a custom variable.

The specified variable ``name`` should not have an existing help string
set. If a help string is already present then ``False`` will be returned
and no changes will occur.

:param name: variable name
:param description: the help string to add. This is user visible, and
                    should be a translated string.

:return: ``True`` if the help string was successfully added

.. seealso:: :py:func:`variableHelpText`

.. versionadded:: 3.22
%End

    static QString variableHelpText( const QString &variableName );
%Docstring
Returns the help text for a specified variable.

:param variableName: name of variable

.. seealso:: :py:func:`helpText`

.. seealso:: :py:func:`addVariableHelpText`
%End

    static QString formatVariableHelp( const QString &description, bool showValue = true, const QVariant &value = QVariant() );
%Docstring
Returns formatted help text for a variable.

:param description: translated description of variable
:param showValue: set to ``True`` to include current value of variable
                  in help text
:param value: current value of variable to show in help text

.. seealso:: :py:func:`helpText`

.. seealso:: :py:func:`variableHelpText`
%End

    static QString group( const QString &group );
%Docstring
Returns the translated name for a function group.

:param group: untranslated group name
%End

    static QString formatPreviewString( const QVariant &value, bool htmlOutput = true, int maximumPreviewLength = 60 );
%Docstring
Formats an expression result for friendly display to the user. Truncates
the result to a sensible length, and presents text representations of
non numeric/text types (e.g., geometries and features).

:param value: expression result to format
:param htmlOutput: set to ``True`` to allow HTML formatting, or
                   ``False`` for plain text output
:param maximumPreviewLength: define the maximum character length of the
                             preview

:return: formatted string, may contain HTML formatting characters if
         ``htmlOutput`` is ``True``
%End

    static QString createFieldEqualityExpression( const QString &fieldName, const QVariant &value, QMetaType::Type fieldType = QMetaType::Type::UnknownType );
%Docstring
Create an expression allowing to evaluate if a field is equal to a
value. The value may be null.

:param fieldName: the name of the field
:param value: the value of the field
:param fieldType: the type of the field on the left side used to quote
                  the value. If not given, the value type is used
                  instead

:return: the expression to evaluate field equality
%End

 static QString createFieldEqualityExpression( const QString &fieldName, const QVariant &value, QVariant::Type fieldType ) /Deprecated/;
%Docstring
Create an expression allowing to evaluate if a field is equal to a
value. The value may be null.

:param fieldName: the name of the field
:param value: the value of the field
:param fieldType: the type of the field on the left side used to quote
                  the value. If not given, the value type is used
                  instead

:return: the expression to evaluate field equality

.. deprecated:: 3.38

   Use the method with a QMetaType.Type argument instead.
%End

    static bool isFieldEqualityExpression( const QString &expression, QString &field /Out/, QVariant &value /Out/ );
%Docstring
Returns ``True`` if the given ``expression`` is a simple "field=value"
type expression.

:param expression: expression to test

:return: - ``True`` if the expression is a field equality expression
         - field: the field name if the expression is a field equality
           expression
         - value: the value if the expression is a field equality
           expression

.. versionadded:: 3.18
%End

    static bool attemptReduceToInClause( const QStringList &expressions, QString &result /Out/ );
%Docstring
Attempts to reduce a list of expressions to a single "field IN (val1,
val2, ... )" type expression.

This will only be possible if all the input expressions form simple
"field=value" OR "field IN (value1, value2)" expressions, and all
reference the same field name.

Returns ``True`` if the given ``expressions`` could be converted to an
IN type expression.

:param expressions: expressions to test

:return: - ``True`` if the expression was converted to a field IN type
           expression
         - result: the calculated "field IN (...)" expression, wherever
           possible

.. versionadded:: 3.18
%End

    SIP_PYOBJECT __repr__();
%MethodCode
    QString str = QStringLiteral( "<QgsExpression: '%1'>" ).arg( sipCpp->expression() );
    sipRes = PyUnicode_FromString( str.toUtf8().constData() );
%End

};


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