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nyalldawsonnyalldawson
committedJul 10, 2017
Move declaration of algorithm parameters/outputs to a new virtual
initAlgorithm() method This allows 2 benefits: - algorithms can be subclassed and have subclasses add additional parameters/outputs to the algorithm. With the previous approach of declaring parameters/outputs in the constructor, it's not possible to call virtual methods to add additional parameters/ outputs (since you can't call virtual methods from a constructor). - initAlgorithm takes a variant map argument, allowing the algorithm to dynamically adjust its declared parameters and outputs according to this configuration map. This potentially allows model algorithms which can be configured to have variable numbers of parameters and outputs at run time. E.g. a "router" algorithm which directs features to one of any number of output sinks depending on some user configured criteria.
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ltr-3_40final-3_0_0
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‎python/core/processing/models/qgsprocessingmodelalgorithm.sip

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -27,6 +27,9 @@ class QgsProcessingModelAlgorithm : QgsProcessingAlgorithm
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Constructor for QgsProcessingModelAlgorithm.
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%End
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virtual void initAlgorithm( const QVariantMap &configuration = QVariantMap() ); //#spellok
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virtual QString name() const;
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virtual QString displayName() const;
@@ -46,8 +49,6 @@ class QgsProcessingModelAlgorithm : QgsProcessingAlgorithm
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virtual QString asPythonCommand( const QVariantMap &parameters, QgsProcessingContext &context ) const;
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virtual QgsProcessingModelAlgorithm *createInstance() const /Factory/;
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void setName( const QString &name );
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%Docstring
@@ -364,6 +365,9 @@ Translated description of variable
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protected:
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virtual QgsProcessingAlgorithm *createInstance() const /Factory/;
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virtual QVariantMap processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback );
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‎python/core/processing/qgsprocessingalgorithm.sip

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Original file line numberDiff line numberDiff line change
@@ -38,6 +38,10 @@ class QgsProcessingAlgorithm
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QgsProcessingAlgorithm();
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%Docstring
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Constructor for QgsProcessingAlgorithm.
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initAlgorithm() should be called after creating an algorithm to ensure it can correctly configure
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its parameterDefinitions() and outputDefinitions(). Alternatively, calling create() will return
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a pre-initialized copy of the algorithm.
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%End
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virtual ~QgsProcessingAlgorithm();
@@ -46,6 +50,11 @@ class QgsProcessingAlgorithm
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QgsProcessingAlgorithm *create() const /Factory/;
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%Docstring
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Creates a copy of the algorithm, ready for execution.
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This method returns a new, preinitialized copy of the algorithm, ready for
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executing.
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.. seealso:: initAlgorithm()
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:rtype: QgsProcessingAlgorithm
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%End
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@@ -345,11 +354,35 @@ class QgsProcessingAlgorithm
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sipTransferTo( resObj, Py_None );
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%End
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virtual void initAlgorithm( const QVariantMap &configuration = QVariantMap() ) = 0;
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%Docstring
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Initializes the algorithm using the specified ``configuration``.
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This should be called directly after creating algorithms and before retrieving
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any parameterDefinitions() or outputDefinitions().
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Subclasses should use their implementations to add all required input parameter and output
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definitions (which can be dynamically adjusted according to ``configuration``).
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Dynamic configuration can be used by algorithms which alter their behavior
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when used inside processing models. For instance, a "feature router" type
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algorithm which sends input features to one of any number of outputs sinks
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based on some preconfigured filter parameters can use the init method to
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create these outputs based on the specified ``configuration``.
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.. seealso:: addParameter()
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.. seealso:: addOutput()
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%End
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bool addParameter( QgsProcessingParameterDefinition *parameterDefinition /Transfer/ );
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%Docstring
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Adds a parameter ``definition`` to the algorithm. Ownership of the definition is transferred to the algorithm.
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Returns true if parameter could be successfully added, or false if the parameter could not be added (e.g.
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as a result of a duplicate name).
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This should usually be called from a subclass' initAlgorithm() implementation.
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.. seealso:: initAlgorithm()
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.. seealso:: addOutput()
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:rtype: bool
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%End
@@ -365,7 +398,11 @@ class QgsProcessingAlgorithm
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Adds an output ``definition`` to the algorithm. Ownership of the definition is transferred to the algorithm.
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Returns true if the output could be successfully added, or false if the output could not be added (e.g.
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as a result of a duplicate name).
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This should usually be called from a subclass' initAlgorithm() implementation.
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.. seealso:: addParameter()
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.. seealso:: initAlgorithm()
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:rtype: bool
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%End
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