QGIS API Documentation 3.28.0-Firenze (ed3ad0430f)
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c++ helper class for defining QgsExpression functions. More...
#include <qgsexpressionfunction.h>
Public Member Functions | |
QgsStaticExpressionFunction (const QString &fnname, const QgsExpressionFunction::ParameterList ¶ms, FcnEval fcn, const QString &group, const QString &helpText, const std::function< bool(const QgsExpressionNodeFunction *node)> &usesGeometry, const std::function< QSet< QString >(const QgsExpressionNodeFunction *node)> &referencedColumns, bool lazyEval=false, const QStringList &aliases=QStringList(), bool handlesNull=false) | |
Static function for evaluation against a QgsExpressionContext, using a named list of parameter values. More... | |
QgsStaticExpressionFunction (const QString &fnname, const QgsExpressionFunction::ParameterList ¶ms, FcnEval fcn, const QString &group, const QString &helpText=QString(), bool usesGeometry=false, const QSet< QString > &referencedColumns=QSet< QString >(), bool lazyEval=false, const QStringList &aliases=QStringList(), bool handlesNull=false) | |
Static function for evaluation against a QgsExpressionContext, using a named list of parameter values. More... | |
QgsStaticExpressionFunction (const QString &fnname, const QgsExpressionFunction::ParameterList ¶ms, FcnEval fcn, const QStringList &groups, const QString &helpText=QString(), bool usesGeometry=false, const QSet< QString > &referencedColumns=QSet< QString >(), bool lazyEval=false, const QStringList &aliases=QStringList(), bool handlesNull=false) | |
Static function for evaluation against a QgsExpressionContext, using a named list of parameter values and list of groups. More... | |
QgsStaticExpressionFunction (const QString &fnname, int params, FcnEval fcn, const QString &group, const QString &helpText=QString(), bool usesGeometry=false, const QSet< QString > &referencedColumns=QSet< QString >(), bool lazyEval=false, const QStringList &aliases=QStringList(), bool handlesNull=false) | |
Static function for evaluation against a QgsExpressionContext, using an unnamed list of parameter values. More... | |
QgsStaticExpressionFunction (const QString &fnname, int params, FcnEval fcn, const QStringList &groups, const QString &helpText=QString(), bool usesGeometry=false, const QSet< QString > &referencedColumns=QSet< QString >(), bool lazyEval=false, const QStringList &aliases=QStringList(), bool handlesNull=false) | |
Static function for evaluation against a QgsExpressionContext, using an unnamed list of parameter values and list of groups. More... | |
QStringList | aliases () const override |
Returns a list of possible aliases for the function. More... | |
QVariant | func (const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction *node) override |
Returns result of evaluating the function. More... | |
bool | isStatic (const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context) const override |
Will be called during prepare to determine if the function is static. More... | |
bool | prepare (const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context) const override |
This will be called during the prepare step() of an expression if it is not static. More... | |
QSet< QString > | referencedColumns (const QgsExpressionNodeFunction *node) const override |
Returns a set of field names which are required for this function. More... | |
void | setIsStatic (bool isStatic) |
Tag this function as either static or not static. More... | |
void | setIsStaticFunction (const std::function< bool(const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext *) > &isStatic) |
Set a function that will be called in the prepare step to determine if the function is static or not. More... | |
void | setPrepareFunction (const std::function< bool(const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext *)> &prepareFunc) |
Set a function that will be called in the prepare step to determine if the function is static or not. More... | |
bool | usesGeometry (const QgsExpressionNodeFunction *node) const override |
Does this function use a geometry object. More... | |
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QgsExpressionFunction (const QString &fnname, const QgsExpressionFunction::ParameterList ¶ms, const QString &group, const QString &helpText=QString(), bool lazyEval=false, bool handlesNull=false, bool isContextual=false) | |
Constructor for function which uses named parameter list. More... | |
QgsExpressionFunction (const QString &fnname, const QgsExpressionFunction::ParameterList ¶ms, const QStringList &groups, const QString &helpText=QString(), bool lazyEval=false, bool handlesNull=false, bool isContextual=false) | |
Constructor for function which uses named parameter list and group list. More... | |
QgsExpressionFunction (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. More... | |
QgsExpressionFunction (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 unnamed parameters and group list. More... | |
virtual | ~QgsExpressionFunction ()=default |
virtual QStringList | aliases () const |
Returns a list of possible aliases for the function. More... | |
virtual QVariant | func (const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction *node)=0 |
Returns result of evaluating the function. More... | |
QString | group () const |
Returns the first group which the function belongs to. More... | |
QStringList | groups () const |
Returns a list of the groups the function belongs to. More... | |
virtual bool | handlesNull () const |
Returns true if the function handles NULL values in arguments by itself, and the default NULL value handling should be skipped. More... | |
const QString | helpText () const |
The help text for the function. More... | |
bool | isContextual () const |
Returns whether the function is only available if provided by a QgsExpressionContext object. More... | |
virtual bool | isDeprecated () const |
Returns true if the function is deprecated and should not be presented as a valid option to users in expression builders. More... | |
virtual bool | isStatic (const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context) const |
Will be called during prepare to determine if the function is static. More... | |
bool | lazyEval () const |
true if this function should use lazy evaluation. More... | |
int | minParams () const |
The minimum number of parameters this function takes. More... | |
QString | name () const |
The name of the function. More... | |
bool | operator== (const QgsExpressionFunction &other) const |
const QgsExpressionFunction::ParameterList & | parameters () const |
Returns the list of named parameters for the function, if set. More... | |
int | params () const |
The number of parameters this function takes. More... | |
virtual bool | prepare (const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context) const |
This will be called during the prepare step() of an expression if it is not static. More... | |
virtual QSet< QString > | referencedColumns (const QgsExpressionNodeFunction *node) const |
Returns a set of field names which are required for this function. More... | |
virtual QVariant | run (QgsExpressionNode::NodeList *args, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction *node) |
Evaluates the function, first evaluating all required arguments before passing them to the function's func() method. More... | |
virtual bool | usesGeometry (const QgsExpressionNodeFunction *node) const |
Does this function use a geometry object. More... | |
Static Public Member Functions | |
static const QList< QgsExpressionFunction * > & | functions () |
Returns a list of all registered expression functions. More... | |
Additional Inherited Members | |
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typedef QVariant(* | FcnEval) (const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction *node) |
Function definition for evaluation against an expression context, using a list of values as parameters to the function. More... | |
typedef QList< QgsExpressionFunction::Parameter > | ParameterList |
List of parameters, used for function definition. More... | |
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static bool | allParamsStatic (const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context) |
This will return true if all the params for the provided function node are static within the constraints imposed by the context within the given parent. More... | |
c++ helper class for defining QgsExpression functions.
Definition at line 349 of file qgsexpressionfunction.h.
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Static function for evaluation against a QgsExpressionContext, using an unnamed list of parameter values.
Definition at line 356 of file qgsexpressionfunction.h.
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Static function for evaluation against a QgsExpressionContext, using an unnamed list of parameter values and list of groups.
Definition at line 378 of file qgsexpressionfunction.h.
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Static function for evaluation against a QgsExpressionContext, using a named list of parameter values.
Definition at line 399 of file qgsexpressionfunction.h.
QgsStaticExpressionFunction::QgsStaticExpressionFunction | ( | const QString & | fnname, |
const QgsExpressionFunction::ParameterList & | params, | ||
FcnEval | fcn, | ||
const QString & | group, | ||
const QString & | helpText, | ||
const std::function< bool(const QgsExpressionNodeFunction *node)> & | usesGeometry, | ||
const std::function< QSet< QString >(const QgsExpressionNodeFunction *node)> & | referencedColumns, | ||
bool | lazyEval = false , |
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const QStringList & | aliases = QStringList() , |
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bool | handlesNull = false |
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Static function for evaluation against a QgsExpressionContext, using a named list of parameter values.
Lambda functions can be provided that will be called to determine if a geometry is used an which columns are referenced. This is only required if this cannot be determined by calling each parameter node's usesGeometry() or referencedColumns() method. For example, an aggregate expression requires the geometry and all columns if the parent variable is used. If nullptr
is passed as a node to these functions, they should stay on the safe side and return if they could potentially require a geometry or columns.
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inline |
Static function for evaluation against a QgsExpressionContext, using a named list of parameter values and list of groups.
Definition at line 442 of file qgsexpressionfunction.h.
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overridevirtual |
Returns a list of possible aliases for the function.
These include other permissible names for the function, e.g., deprecated names.
Reimplemented from QgsExpressionFunction.
Definition at line 191 of file qgsexpressionfunction.cpp.
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inlineoverridevirtual |
Returns result of evaluating the function.
values | list of values passed to the function |
context | context expression is being evaluated against |
parent | parent expression |
node | function node |
Implements QgsExpressionFunction.
Definition at line 467 of file qgsexpressionfunction.h.
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static |
Returns a list of all registered expression functions.
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overridevirtual |
Will be called during prepare to determine if the function is static.
A function is static if it will return the same value for every feature with different attributes and/or geometry.
By default this will return true
, if all arguments that have been passed to the function are also static.
Reimplemented from QgsExpressionFunction.
Definition at line 212 of file qgsexpressionfunction.cpp.
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overridevirtual |
This will be called during the prepare step() of an expression if it is not static.
This can be used by functions to do any preparation steps that might help to speedup the upcoming evaluation.
Reimplemented from QgsExpressionFunction.
Definition at line 220 of file qgsexpressionfunction.cpp.
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overridevirtual |
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.
Reimplemented from QgsExpressionFunction.
Definition at line 204 of file qgsexpressionfunction.cpp.
void QgsStaticExpressionFunction::setIsStatic | ( | bool | isStatic | ) |
Tag this function as either static or not static.
This will indicate that the function is always expected to return the same value for an iteration (or explicitly request that it's going to be called for every feature, if false
).
Definition at line 233 of file qgsexpressionfunction.cpp.
void QgsStaticExpressionFunction::setIsStaticFunction | ( | const std::function< bool(const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext *) > & | isStatic | ) |
Set a function that will be called in the prepare step to determine if the function is static or not.
By default this is set to a function that checks all arguments that have been passed to the variable and if all of them are static, it will be assumed that the function is static as well.
Definition at line 228 of file qgsexpressionfunction.cpp.
void QgsStaticExpressionFunction::setPrepareFunction | ( | const std::function< bool(const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext *)> & | prepareFunc | ) |
Set a function that will be called in the prepare step to determine if the function is static or not.
By default this is set to a function that checks all arguments that have been passed to the variable and if all of them are static, it will be assumed that the function is static as well.
Definition at line 239 of file qgsexpressionfunction.cpp.
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overridevirtual |
Does this function use a geometry object.
Reimplemented from QgsExpressionFunction.
Definition at line 196 of file qgsexpressionfunction.cpp.