class QgsExpression
{
%TypeHeaderCode
#include "qgsexpression.h"
%End
public:
/**
* Creates a new expression based on the provided string.
* The string will immediately be parsed. For optimization
* {@link prepare()} should alwys be called before every
* loop in which this expression is used.
*/
QgsExpression( const QString& expr );
/**
* Create an empty expression.
*
* @note Added in QGIS 3.0
*/
QgsExpression();
~QgsExpression();
/**
* Checks if this expression is valid.
* A valid expression could be parsed but does not necessarily evaluate properly.
*
* @note Added in QGIS 3.0
*/
bool isValid() const;
//! Returns true if an error occurred when parsing the input expression
bool hasParserError() const;
//! Returns parser error
QString parserErrorString() const;
//! Returns root node of the expression. Root node is null is parsing has failed
const QgsExpression::Node* rootNode() const;
/** Get the expression ready for evaluation - find out column indexes.
* @param context context for preparing expression
* @note added in QGIS 2.12
*/
bool prepare( const QgsExpressionContext *context );
/**
* Get list of columns referenced by the expression.
*
* @note If the returned list contains the QgsFeatureRequest::AllAttributes constant then
* all attributes from the layer are required for evaluation of the expression.
* QgsFeatureRequest::setSubsetOfAttributes automatically handles this case.
*
* @see referencedAttributeIndexes()
*/
QSet<QString> referencedColumns() const;
/**
* Return a list of all variables which are used in this expression.
*/
QSet<QString> referencedVariables() const;
/**
* Return a list of field name indexes obtained from the provided fields.
*
* @note Added in QGIS 3.0
*/
QSet<int> referencedAttributeIndexes( const QgsFields& fields ) const;
//! Returns true if the expression uses feature geometry for some computation
bool needsGeometry() const;
// evaluation
/** Evaluate the feature and return the result.
* @note this method does not expect that prepare() has been called on this instance
* @note added in QGIS 2.12
*/
QVariant evaluate();
/** Evaluate the expression against the specified context and return the result.
* @param context context for evaluating expression
* @note prepare() should be called before calling this method.
* @note added in QGIS 2.12
*/
QVariant evaluate( const QgsExpressionContext* context );
//! Returns true if an error occurred when evaluating last input
bool hasEvalError() const;
//! Returns evaluation error
QString evalErrorString() const;
//! Set evaluation error (used internally by evaluation functions)
void setEvalErrorString( const QString& str );
/** Checks whether an expression consists only of a single field reference
* @note added in 2.9
*/
bool isField() const;
/** Tests whether a string is a valid expression.
* @param text string to test
* @param context optional expression context
* @param errorMessage will be filled with any error message from the validation
* @returns true if string is a valid expression
* @note added in QGIS 3.0
*/
static bool checkExpression( const QString& text, const QgsExpressionContext* context, QString &errorMessage /Out/ );
/**
* Set the expression string, will reset the whole internal structure.
*
* @note Added in QGIS 3.0
*/
void setExpression( const QString& expression );
//! Return the original, unmodified expression string.
//! If there was none supplied because it was constructed by sole
//! API calls, dump() will be used to create one instead.
QString expression() const;
//! Return an expression string, constructed from the internal
//! abstract syntax tree. This does not contain any nice whitespace
//! formatting or comments. In general it is preferrable to use
//! expression() instead.
QString dump() const;
/** Return calculator used for distance and area calculations
* (used by $length, $area and $perimeter functions only)
* @see setGeomCalculator()
* @see distanceUnits()
*/
QgsDistanceArea *geomCalculator();
/** Sets the geometry calculator used for distance and area calculations in expressions.
* (used by $length, $area and $perimeter functions only). By default, no geometry
* calculator is set and all distance and area calculations are performed using simple
* cartesian methods (ie no ellipsoidal calculations).
* @param calc geometry calculator. Ownership is not transferred. Set to a nullptr to force
* cartesian calculations.
* @see geomCalculator()
*/
void setGeomCalculator( const QgsDistanceArea* calc );
/** Returns the desired distance units for calculations involving geomCalculator(), eg "$length" and "$perimeter".
* @note distances are only converted when a geomCalculator() has been set
* @note added in QGIS 2.14
* @see setDistanceUnits()
*/
QgsUnitTypes::DistanceUnit distanceUnits() const;
/** Sets the desired distance units for calculations involving geomCalculator(), eg "$length" and "$perimeter".
* @note distances are only converted when a geomCalculator() has been set
* @note added in QGIS 2.14
* @see distanceUnits()
*/
void setDistanceUnits( QgsUnitTypes::DistanceUnit unit );
/** Returns the desired areal units for calculations involving geomCalculator(), eg "$area".
* @note areas are only converted when a geomCalculator() has been set
* @note added in QGIS 2.14
* @see setAreaUnits()
* @see distanceUnits()
*/
QgsUnitTypes::AreaUnit areaUnits() const;
/** Sets the desired areal units for calculations involving geomCalculator(), eg "$area".
* @note areas are only converted when a geomCalculator() has been set
* @note added in QGIS 2.14
* @see areaUnits()
* @see setDistanceUnits()
*/
void setAreaUnits( QgsUnitTypes::AreaUnit unit );
/** 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
* @param context expression context
* @param distanceArea optional QgsDistanceArea. If specified, the QgsDistanceArea is used for distance
* and area conversion
* @note added in QGIS 2.12
*/
static QString replaceExpressionText( const QString &action, const QgsExpressionContext* context,
const QgsDistanceArea* distanceArea = 0 );
/** 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
* @returns evaluated double value, or fallback value
* @note added in QGIS 2.7
* @note this method is inefficient for bulk evaluation of expressions, it is intended
* for one-off evaluations only.
*/
static double evaluateToDouble( const QString& text, const double fallbackValue );
/**
* @brief list of unary operators
* @note if any change is made here, the definition of QgsExpression::UnaryOperatorText[] must be adapted.
*/
enum UnaryOperator
{
uoNot,
uoMinus,
};
/**
* @brief list of binary operators
* @note if any change is made here, the definition of QgsExpression::BinaryOperatorText[] must be adapted.
*/
enum BinaryOperator
{
// logical
boOr,
boAnd,
// comparison
boEQ, // =
boNE, // <>
boLE, // <=
boGE, // >=
boLT, // <
boGT, // >
boRegexp,
boLike,
boNotLike,
boILike,
boNotILike,
boIs,
boIsNot,
// math
boPlus,
boMinus,
boMul,
boDiv,
boIntDiv,
boMod,
boPow,
// strings
boConcat,
};
enum SpatialOperator
{
soBbox,
soIntersects,
soContains,
soCrosses,
soEquals,
soDisjoint,
soOverlaps,
soTouches,
soWithin,
};
//! @note not available in Python bindings
// static const char* BinaryOperatorText[];
//! @note not available in Python bindings
// static const char* UnaryOperatorText[];
/**
* Represents a single parameter passed to a function.
* \note added in QGIS 2.16
*/
class Parameter
{
public:
/** Constructor for Parameter.
* @param name parameter name, used when named parameter are specified in an expression
* @param optional set to true if parameter should be optional
* @param defaultValue default value to use for optional parameters
*/
Parameter( const QString& name,
bool optional = false,
const QVariant& defaultValue = QVariant() );
//! Returns the name of the parameter.
QString name() const;
//! Returns true if the parameter is optional.
bool optional() const;
//! Returns the default value for the parameter.
QVariant defaultValue() const;
bool operator==( const QgsExpression::Parameter& other ) const;
};
//! List of parameters, used for function definition
typedef QList< QgsExpression::Parameter > ParameterList;
/**
* A abstract base class for defining QgsExpression functions.
*/
class Function
{
public:
//! Constructor for function which uses unnamed parameters
Function( const QString& fnname,
int params,
const QString& group,
const QString& helpText = QString(),
bool lazyEval = false,
bool handlesNull = false,
bool isContextual = false );
/** Constructor for function which uses unnamed parameters and group list
* @note added in QGIS 3.0
*/
Function( const QString& fnname,
int params,
const QStringList& groups,
const QString& helpText = QString(),
bool lazyEval = false,
bool handlesNull = false,
bool isContextual = false );
/** Constructor for function which uses named parameter list.
* @note added in QGIS 2.16
*/
Function( const QString& fnname,
const QgsExpression::ParameterList& params,
const QString& group,
const QString& helpText = QString(),
bool lazyEval = false,
bool handlesNull = false,
bool isContextual = false );
/** Constructor for function which uses named parameter list and group list.
* @note added in QGIS 3.0
*/
Function( const QString& fnname,
const QgsExpression::ParameterList& params,
const QStringList& groups,
const QString& helpText = QString(),
bool lazyEval = false,
bool handlesNull = false,
bool isContextual = false );
virtual ~Function();
/** The name of the function. */
QString name() const;
/** The number of parameters this function takes. */
int params() const;
/** The mininum number of parameters this function takes. */
int minParams() const;
/** Returns the list of named parameters for the function, if set.
* @note added in QGIS 2.16
*/
const QgsExpression::ParameterList& parameters() const;
//! Does this function use a geometry object.
virtual bool usesGeometry( const QgsExpression::NodeFunction* node ) const;
/** Returns a list of possible aliases for the function. These include
* other permissible names for the function, eg deprecated names.
* @return list of known aliases
* @note added in QGIS 2.9
*/
virtual QStringList aliases() const;
/** True if this function should use lazy evaluation. Lazy evaluation functions take QgsExpression::Node objects
* rather than the node results when called. You can use node->eval(parent, feature) to evaluate the node and return the result
* Functions are non lazy default and will be given the node return value when called
*/
bool lazyEval() const;
/**
* Returns a set of field names which are required for this function.
* May contain QgsFeatureRequest::AllAttributes to signal that all
* attributes are required.
* If in doubt this will return more fields than strictly required.
*
* @note Added in QGIS 3.0
*/
virtual QSet<QString> referencedColumns( const QgsExpression::NodeFunction* node ) const;
/** Returns whether the function is only available if provided by a QgsExpressionContext object.
* @note added in QGIS 2.12
*/
bool isContextual() const;
/** Returns true if the function is deprecated and should not be presented as a valid option
* to users in expression builders.
* @note added in QGIS 3.0
*/
virtual bool isDeprecated() const;
/** Returns the first group which the function belongs to.
* @note consider using groups() instead, as some functions naturally belong in multiple groups
*/
QString group() const;
/** Returns a list of the groups the function belongs to.
* @note added in QGIS 3.0
* @see group()
*/
QStringList groups() const;
/** The help text for the function. */
const QString helpText() const;
/** Returns result of evaluating the function.
* @param values list of values passed to the function
* @param context context expression is being evaluated against
* @param parent parent expression
* @returns result of function
*/
virtual QVariant func( const QVariantList& values, const QgsExpressionContext* context, QgsExpression* parent ) = 0;
virtual bool handlesNull() const;
};
static const QList<QgsExpression::Function *>& Functions();
static const QStringList& BuiltinFunctions();
/** Registers a function to the expression engine. This is required to allow expressions to utilise the function.
* @param function function to register
* @param transferOwnership set to true to transfer ownership of function to expression engine
* @returns true on successful registration
* @see unregisterFunction
*/
static bool registerFunction( Function* function );
/** Unregisters a function from the expression engine. The function will no longer be usable in expressions.
* @param name function name
* @see registerFunction
*/
static bool unregisterFunction( const QString& name );
/** Deletes all registered functions whose ownership have been transferred to the expression engine.
* @note added in QGIS 2.12
*/
static void cleanRegisteredFunctions();
//! tells whether the identifier is a name of existing function
static bool isFunctionName( const QString& name );
//! return index of the function in Functions array
static int functionIndex( const QString& name );
/** Returns the number of functions defined in the parser
* @return The number of function defined in the parser.
*/
static int functionCount();
/** Returns a quoted column reference (in double quotes)
* @see quotedString()
* @see quotedValue()
*/
static QString quotedColumnRef( QString name );
/** Returns a quoted version of a string (in single quotes)
* @see quotedValue()
* @see quotedColumnRef()
*/
static QString quotedString( QString text );
/** Returns a string representation of a literal value, including appropriate
* quotations where required.
* @param value value to convert to a string representation
* @note added in QGIS 2.14
* @see quotedString()
* @see quotedColumnRef()
*/
static QString quotedValue( const QVariant& value );
/** 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
* @note added in QGIS 2.14
* @see quotedString()
* @see quotedColumnRef()
*/
static QString quotedValue( const QVariant& value, QVariant::Type type );
//////
enum NodeType
{
ntUnaryOperator,
ntBinaryOperator,
ntInOperator,
ntFunction,
ntLiteral,
ntColumnRef,
ntCondition
};
class Node
{
%ConvertToSubClassCode
switch (sipCpp->nodeType())
{
case QgsExpression::ntUnaryOperator: sipType = sipType_QgsExpression_NodeUnaryOperator; break;
case QgsExpression::ntBinaryOperator: sipType = sipType_QgsExpression_NodeBinaryOperator; break;
case QgsExpression::ntInOperator: sipType = sipType_QgsExpression_NodeInOperator; break;
case QgsExpression::ntFunction: sipType = sipType_QgsExpression_NodeFunction; break;
case QgsExpression::ntLiteral: sipType = sipType_QgsExpression_NodeLiteral; break;
case QgsExpression::ntColumnRef: sipType = sipType_QgsExpression_NodeColumnRef; break;
case QgsExpression::ntCondition: sipType = sipType_QgsExpression_NodeCondition; break;
default: sipType = 0; break;
}
%End
public:
virtual ~Node();
/**
* Abstract virtual that returns the type of this node.
*
* @return The type of this node
*/
virtual QgsExpression::NodeType nodeType() const = 0;
/**
* Abstract virtual eval method
* Errors are reported to the parent
* @note added in QGIS 2.12
*/
virtual QVariant eval( QgsExpression* parent, const QgsExpressionContext* context ) = 0;
/**
* Abstract virtual preparation method
* Errors are reported to the parent
* @note added in QGIS 2.12
*/
virtual bool prepare( QgsExpression* parent, const QgsExpressionContext* context ) = 0;
/**
* Abstract virtual dump method
*
* @return An expression which represents this node as string
*/
virtual QString dump() const = 0;
/**
* Generate a clone of this node.
* Make sure that the clone does not contain any information which is
* generated in prepare and context related.
* Ownership is transferred to the caller.
*
* @return a deep copy of this node.
*/
virtual QgsExpression::Node* clone() const = 0;
/**
* Abstract virtual method which returns a list of columns required to
* evaluate this node.
*
* When reimplementing this, you need to return any column that is required to
* evaluate this node and in addition recursively collect all the columns required
* to evaluate child nodes.
*
* @return A list of columns required to evaluate this expression
*/
virtual QSet<QString> referencedColumns() const = 0;
/**
* Return a list of all variables which are used in this expression.
*/
virtual QSet<QString> referencedVariables() const = 0;
/**
* Abstract virtual method which returns if the geometry is required to evaluate
* this expression.
*
* This needs to call `needsGeometry()` recursively on any child nodes.
*
* @return true if a geometry is required to evaluate this expression
*/
virtual bool needsGeometry() const = 0;
};
//! Named node
//! @note added in QGIS 2.16
class NamedNode
{
public:
/** Constructor for NamedNode
* @param name node name
* @param node node
*/
NamedNode( const QString& name, QgsExpression::Node* node );
//! Node name
QString name;
//! Node
QgsExpression::Node* node;
};
class NodeList
{
public:
NodeList();
~NodeList();
/** Takes ownership of the provided node */
void append( QgsExpression::Node* node /Transfer/ );
/** Adds a named node. Takes ownership of the provided node.
* @note added in QGIS 2.16
*/
void append( QgsExpression::NamedNode* node /Transfer/ );
/** Returns the number of nodes in the list.
*/
int count() const;
//! Returns true if list contains any named nodes
//! @note added in QGIS 2.16
bool hasNamedNodes() const;
/**
* Get a list of all the nodes.
*/
QList<QgsExpression::Node*> list();
/**
* Get the node at position i in the list.
*
* @note Added in QGIS 3.0
*/
QgsExpression::Node* at( int i );
//! Returns a list of names for nodes. Unnamed nodes will be indicated by an empty string in the list.
//! @note added in QGIS 2.16
QStringList names() const;
/** Creates a deep copy of this list. Ownership is transferred to the caller */
QgsExpression::NodeList* clone() const;
virtual QString dump() const;
};
class NodeUnaryOperator : QgsExpression::Node
{
public:
NodeUnaryOperator( QgsExpression::UnaryOperator op, QgsExpression::Node* operand /Transfer/ );
~NodeUnaryOperator();
QgsExpression::UnaryOperator op() const;
QgsExpression::Node* operand() const;
virtual QgsExpression::NodeType nodeType() const;
virtual bool prepare( QgsExpression* parent, const QgsExpressionContext* context );
virtual QVariant eval( QgsExpression* parent, const QgsExpressionContext* context );
virtual QString dump() const;
virtual QSet<QString> referencedColumns() const;
virtual QSet<QString> referencedVariables() const;
virtual bool needsGeometry() const;
virtual QgsExpression::Node* clone() const;
};
class NodeBinaryOperator : QgsExpression::Node
{
public:
NodeBinaryOperator( QgsExpression::BinaryOperator op, QgsExpression::Node* opLeft /Transfer/, QgsExpression::Node* opRight /Transfer/ );
~NodeBinaryOperator();
QgsExpression::BinaryOperator op() const;
QgsExpression::Node* opLeft() const;
QgsExpression::Node* opRight() const;
virtual QgsExpression::NodeType nodeType() const;
virtual bool prepare( QgsExpression* parent, const QgsExpressionContext* context );
virtual QVariant eval( QgsExpression* parent, const QgsExpressionContext* context );
virtual QString dump() const;
virtual QSet<QString> referencedColumns() const;
virtual QSet<QString> referencedVariables() const;
virtual bool needsGeometry() const;
virtual QgsExpression::Node* clone() const;
int precedence() const;
bool leftAssociative() const;
protected:
bool compare( double diff );
int computeInt( int x, int y );
double computeDouble( double x, double y );
/** Computes the result date time calculation from a start datetime and an interval
* @param d start datetime
* @param i interval to add or subtract (depending on mOp)
*/
QDateTime computeDateTimeFromInterval( const QDateTime& d, QgsInterval *i );
};
class NodeInOperator : QgsExpression::Node
{
public:
NodeInOperator( QgsExpression::Node* node /Transfer/, QgsExpression::NodeList* list /Transfer/, bool notin = false );
~NodeInOperator();
QgsExpression::Node* node() const;
bool isNotIn() const;
QgsExpression::NodeList* list() const;
virtual QgsExpression::NodeType nodeType() const;
virtual bool prepare( QgsExpression* parent, const QgsExpressionContext* context );
virtual QVariant eval( QgsExpression* parent, const QgsExpressionContext* context );
virtual QString dump() const;
virtual QSet<QString> referencedColumns() const;
virtual QSet<QString> referencedVariables() const;
virtual bool needsGeometry() const;
virtual QgsExpression::Node* clone() const;
};
class NodeFunction : QgsExpression::Node
{
public:
NodeFunction( int fnIndex, QgsExpression::NodeList* args /Transfer/ );
//NodeFunction( QString name, QgsExpression::NodeList* args );
~NodeFunction();
int fnIndex() const;
QgsExpression::NodeList* args() const;
virtual QgsExpression::NodeType nodeType() const;
virtual bool prepare( QgsExpression* parent, const QgsExpressionContext* context );
virtual QVariant eval( QgsExpression* parent, const QgsExpressionContext* context );
virtual QString dump() const;
virtual QSet<QString> referencedColumns() const;
virtual QSet<QString> referencedVariables() const;
virtual bool needsGeometry() const;
virtual QgsExpression::Node* clone() const;
//! Tests whether the provided argument list is valid for the matching function
static bool validateParams( int fnIndex, QgsExpression::NodeList* args, QString& error );
};
class NodeLiteral : QgsExpression::Node
{
public:
NodeLiteral( const QVariant& value );
/** The value of the literal. */
const QVariant& value() const;
virtual QgsExpression::NodeType nodeType() const;
virtual bool prepare( QgsExpression* parent, const QgsExpressionContext* context );
virtual QVariant eval( QgsExpression* parent, const QgsExpressionContext* context );
virtual QString dump() const;
virtual QgsExpression::Node* clone() const;
virtual QSet<QString> referencedColumns() const;
virtual QSet<QString> referencedVariables() const;
virtual bool needsGeometry() const;
};
class NodeColumnRef : QgsExpression::Node
{
public:
NodeColumnRef( const QString& name );
/** The name of the column. */
QString name() const;
virtual QgsExpression::NodeType nodeType() const;
virtual bool prepare( QgsExpression* parent, const QgsExpressionContext* context );
virtual QVariant eval( QgsExpression* parent, const QgsExpressionContext* context );
virtual QString dump() const;
virtual QSet<QString> referencedColumns() const;
virtual QSet<QString> referencedVariables() const;
virtual bool needsGeometry() const;
virtual QgsExpression::Node* clone() const;
};
class WhenThen
{
public:
WhenThen( QgsExpression::Node* whenExp /Transfer/, QgsExpression::Node* thenExp /Transfer/ );
~WhenThen();
//protected:
QgsExpression::Node* mWhenExp;
QgsExpression::Node* mThenExp;
private:
WhenThen( const QgsExpression::WhenThen& rh );
};
class NodeCondition : QgsExpression::Node
{
public:
NodeCondition( QList<QgsExpression::WhenThen*> *conditions, QgsExpression::Node* elseExp = 0 );
~NodeCondition();
virtual QgsExpression::NodeType nodeType() const;
virtual QVariant eval( QgsExpression* parent, const QgsExpressionContext* context );
virtual bool prepare( QgsExpression* parent, const QgsExpressionContext* context );
virtual QString dump() const;
virtual QSet<QString> referencedColumns() const;
virtual QSet<QString> referencedVariables() const;
virtual bool needsGeometry() const;
virtual QgsExpression::Node* clone() const;
};
/** Returns the help text for a specified function.
* @param name function name
* @see variableHelpText()
*/
static QString helpText( QString name );
/** Returns the help text for a specified variable.
* @param variableName name 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
* @see helpText()
* @note added in QGIS 2.12
*/
static QString variableHelpText( const QString& variableName, bool showValue = true, const QVariant& value = QVariant() );
/** Returns the translated name for a function group.
* @param group untranslated group name
*/
static QString group( const QString& group );
/** 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 (eg geometries and features).
* @param value expression result to format
* @returns formatted string, may contain HTML formatting characters
* @note added in QGIS 2.14
*/
static QString formatPreviewString( const QVariant& value );
protected:
void initGeomCalculator();
};