QGIS API Documentation 3.41.0-Master (d5b93354e9c)
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An expression node which takes it value from a feature's field. More...
#include <qgsexpressionnodeimpl.h>
Public Member Functions | |
QgsExpressionNodeColumnRef (const QString &name) | |
Constructor for QgsExpressionNodeColumnRef, referencing the column with the specified name. | |
QgsExpressionNode * | clone () const override |
Generate a clone of this node. | |
QString | dump () const override |
Dump this node into a serialized (part) of an expression. | |
QVariant | evalNode (QgsExpression *parent, const QgsExpressionContext *context) override |
Abstract virtual eval method Errors are reported to the parent. | |
bool | isStatic (QgsExpression *parent, const QgsExpressionContext *context) const override |
Returns true if this node can be evaluated for a static value. | |
QString | name () const |
The name of the column. | |
bool | needsGeometry () const override |
Abstract virtual method which returns if the geometry is required to evaluate this expression. | |
QList< const QgsExpressionNode * > | nodes () const override |
Returns a list of all nodes which are used in this expression. | |
QgsExpressionNode::NodeType | nodeType () const override |
Gets the type of this node. | |
bool | prepareNode (QgsExpression *parent, const QgsExpressionContext *context) override |
Abstract virtual preparation method Errors are reported to the parent. | |
QSet< QString > | referencedColumns () const override |
Abstract virtual method which returns a list of columns required to evaluate this node. | |
QSet< QString > | referencedFunctions () const override |
Returns a set of all functions which are used in this expression. | |
QSet< QString > | referencedVariables () const override |
Returns a set of all variables which are used in this expression. | |
Public Member Functions inherited from QgsExpressionNode | |
virtual | ~QgsExpressionNode ()=default |
QVariant | cachedStaticValue () const |
Returns the node's static cached value. | |
const QgsExpressionNode * | effectiveNode () const |
Returns a reference to the simplest node which represents this node, after any compilation optimizations have been applied. | |
QVariant | eval (QgsExpression *parent, const QgsExpressionContext *context) |
Evaluate this node with the given context and parent. | |
bool | hasCachedStaticValue () const |
Returns true if the node can be replaced by a static cached value. | |
bool | prepare (QgsExpression *parent, const QgsExpressionContext *context) |
Prepare this node for evaluation. | |
void | setCachedStaticValue (const QVariant &value) const |
Sets the cached static value for the node. | |
Additional Inherited Members | |
Public Types inherited from QgsExpressionNode | |
enum | NodeType { ntUnaryOperator , ntBinaryOperator , ntInOperator , ntFunction , ntLiteral , ntColumnRef , ntCondition , ntIndexOperator , ntBetweenOperator } |
Known node types. More... | |
Public Attributes inherited from QgsExpressionNode | |
int | parserFirstColumn = 0 |
First column in the parser this node was found. | |
int | parserFirstLine = 0 |
First line in the parser this node was found. | |
int | parserLastColumn = 0 |
Last column in the parser this node was found. | |
int | parserLastLine = 0 |
Last line in the parser this node was found. | |
Protected Member Functions inherited from QgsExpressionNode | |
QgsExpressionNode ()=default | |
QgsExpressionNode (const QgsExpressionNode &other) | |
void | cloneTo (QgsExpressionNode *target) const |
Copies the members of this node to the node provided in target. | |
QgsExpressionNode & | operator= (const QgsExpressionNode &other) |
Protected Attributes inherited from QgsExpressionNode | |
QVariant | mCachedStaticValue |
Contains the static, precalculated value for the node if mHasCachedValue is true . | |
std::unique_ptr< QgsExpressionNode > | mCompiledSimplifiedNode |
Contains a compiled node which represents a simplified version of this node as a result of compilation optimizations. | |
bool | mHasCachedValue = false |
true if the node has a static, precalculated value. | |
An expression node which takes it value from a feature's field.
Definition at line 512 of file qgsexpressionnodeimpl.h.
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inline |
Constructor for QgsExpressionNodeColumnRef, referencing the column with the specified name.
Definition at line 520 of file qgsexpressionnodeimpl.h.
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overridevirtual |
Generate a clone of this node.
Ownership is transferred to the caller.
Implements QgsExpressionNode.
Definition at line 1695 of file qgsexpressionnodeimpl.cpp.
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overridevirtual |
Dump this node into a serialized (part) of an expression.
The returned expression does not necessarily literally match the original expression, it's just guaranteed to behave the same way.
Implements QgsExpressionNode.
Definition at line 1661 of file qgsexpressionnodeimpl.cpp.
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overridevirtual |
Abstract virtual eval method Errors are reported to the parent.
Implements QgsExpressionNode.
Definition at line 1599 of file qgsexpressionnodeimpl.cpp.
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overridevirtual |
Returns true
if this node can be evaluated for a static value.
This is used during the prepare() step and in case it returns true
, the value of this node will already be evaluated and the result cached (and therefore not re-evaluated in subsequent calls to eval()). In case this returns true
, prepareNode() will never be called.
Implements QgsExpressionNode.
Definition at line 1702 of file qgsexpressionnodeimpl.cpp.
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inline |
The name of the column.
Definition at line 534 of file qgsexpressionnodeimpl.h.
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overridevirtual |
Abstract virtual method which returns if the geometry is required to evaluate this expression.
This needs to call needsGeometry()
recursively on any child nodes.
true
if a geometry is required to evaluate this expression Implements QgsExpressionNode.
Definition at line 1690 of file qgsexpressionnodeimpl.cpp.
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overridevirtual |
Returns a list of all nodes which are used in this expression.
Implements QgsExpressionNode.
Definition at line 1683 of file qgsexpressionnodeimpl.cpp.
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overridevirtual |
Gets the type of this node.
Implements QgsExpressionNode.
Definition at line 1634 of file qgsexpressionnodeimpl.cpp.
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overridevirtual |
Abstract virtual preparation method Errors are reported to the parent.
Implements QgsExpressionNode.
Definition at line 1639 of file qgsexpressionnodeimpl.cpp.
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overridevirtual |
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.
Implements QgsExpressionNode.
Definition at line 1668 of file qgsexpressionnodeimpl.cpp.
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overridevirtual |
Returns a set of all functions which are used in this expression.
Implements QgsExpressionNode.
Definition at line 1678 of file qgsexpressionnodeimpl.cpp.
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overridevirtual |
Returns a set of all variables which are used in this expression.
Implements QgsExpressionNode.
Definition at line 1673 of file qgsexpressionnodeimpl.cpp.