QGIS API Documentation  3.27.0-Master (e113457133)
qgsfeatureiterator.h
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1 /***************************************************************************
2  qgsfeatureiterator.h
3  ---------------------
4  begin : Juli 2012
5  copyright : (C) 2012 by Martin Dobias
6  email : wonder dot sk at gmail dot com
7  ***************************************************************************
8  * *
9  * This program is free software; you can redistribute it and/or modify *
10  * it under the terms of the GNU General Public License as published by *
11  * the Free Software Foundation; either version 2 of the License, or *
12  * (at your option) any later version. *
13  * *
14  ***************************************************************************/
15 #ifndef QGSFEATUREITERATOR_H
16 #define QGSFEATUREITERATOR_H
17 
18 #include "qgis_core.h"
19 #include "qgsfeaturerequest.h"
20 #include "qgsindexedfeature.h"
21 
22 class QgsFeedback;
23 
28 class CORE_EXPORT QgsAbstractFeatureIterator
29 {
30  public:
31 
34  {
38  };
39 
42 
44  virtual ~QgsAbstractFeatureIterator() = default;
45 
47  virtual bool nextFeature( QgsFeature &f );
48 
50  virtual bool rewind() = 0;
52  virtual bool close() = 0;
53 
63  virtual void setInterruptionChecker( QgsFeedback *interruptionChecker ) SIP_SKIP;
64 
69  CompileStatus compileStatus() const { return mCompileStatus; }
70 
81  virtual bool isValid() const
82  {
83  return mValid;
84  }
85 
92  bool compileFailed() const;
93 
99  enum class RequestToSourceCrsResult : int
100  {
101  Success,
102  DistanceWithinMustBeCheckedManually,
103  };
104 
105  protected:
106 
114  virtual bool fetchFeature( QgsFeature &f ) = 0;
115 
126  virtual bool nextFeatureFilterExpression( QgsFeature &f );
127 
139  virtual bool nextFeatureFilterFids( QgsFeature &f );
140 
149  void geometryToDestinationCrs( QgsFeature &feature, const QgsCoordinateTransform &transform ) const;
150 
151 
161  QgsRectangle filterRectToSourceCrs( const QgsCoordinateTransform &transform ) const SIP_THROW( QgsCsException );
162 
175  RequestToSourceCrsResult updateRequestToSourceCrs( QgsFeatureRequest &request, const QgsCoordinateTransform &transform ) const SIP_THROW( QgsCsException );
176 
179 
181  bool mClosed = false;
182 
190  bool mZombie = false;
191 
192  // TODO QGIS 4: make this private
193 
197  int refs = 0;
199  void ref();
201  void deref();
202  friend class QgsFeatureIterator;
203 
205  long long mFetchedCount = 0;
206 
208  CompileStatus mCompileStatus = NoCompilation;
209 
210  bool mCompileFailed = false;
211 
213  virtual bool prepareSimplification( const QgsSimplifyMethod &simplifyMethod );
214 
223  bool mValid = true;
224 
225  private:
226  bool mUseCachedFeatures = false;
227  QList<QgsIndexedFeature> mCachedFeatures;
228  QList<QgsIndexedFeature>::ConstIterator mFeatureIterator;
229 
231  virtual bool providerCanSimplify( QgsSimplifyMethod::MethodType methodType ) const;
232 
241  virtual bool prepareOrderBy( const QList<QgsFeatureRequest::OrderByClause> &orderBys );
242 
249  void setupOrderBy( const QList<QgsFeatureRequest::OrderByClause> &orderBys );
250 };
251 
252 
258 template<typename T>
260 {
261  public:
262  QgsAbstractFeatureIteratorFromSource( T *source, bool ownSource, const QgsFeatureRequest &request )
263  : QgsAbstractFeatureIterator( request )
264  , mSource( source )
265  , mOwnSource( ownSource )
266  {
267  mSource->iteratorOpened( this );
268  }
269 
271  {
272  if ( mOwnSource )
273  delete mSource;
274  }
275 
276  protected:
278  void iteratorClosed() { mSource->iteratorClosed( this ); }
279 
280  T *mSource = nullptr;
282 };
283 
284 
289 class CORE_EXPORT QgsFeatureIterator
290 {
291  public:
292 
293 #ifdef SIP_RUN
294  QgsFeatureIterator *__iter__();
295  % MethodCode
296  sipRes = sipCpp;
297  % End
298 
299  SIP_PYOBJECT __next__() SIP_TYPEHINT( QgsFeature );
300  % MethodCode
301  std::unique_ptr< QgsFeature > f = std::make_unique< QgsFeature >();
302  bool result = false;
303  Py_BEGIN_ALLOW_THREADS
304  result = ( sipCpp->nextFeature( *f ) );
305  Py_END_ALLOW_THREADS
306  if ( result )
307  sipRes = sipConvertFromType( f.release(), sipType_QgsFeature, Py_None );
308  else
309  {
310  PyErr_SetString( PyExc_StopIteration, "" );
311  }
312  % End
313 #endif
314 
316  QgsFeatureIterator() = default;
323 
324  QgsFeatureIterator &operator=( const QgsFeatureIterator &other );
325 
326  bool nextFeature( QgsFeature &f );
327  bool rewind();
328  bool close();
329 
339  bool isValid() const;
340 
342  bool isClosed() const;
343 
352  void setInterruptionChecker( QgsFeedback *interruptionChecker ) SIP_SKIP;
353 
358  QgsAbstractFeatureIterator::CompileStatus compileStatus() const { return mIter->compileStatus(); }
359 
366  bool compileFailed() const { return mIter->compileFailed(); }
367 
368  friend bool operator== ( const QgsFeatureIterator &fi1, const QgsFeatureIterator &fi2 ) SIP_SKIP;
369  friend bool operator!= ( const QgsFeatureIterator &fi1, const QgsFeatureIterator &fi2 ) SIP_SKIP;
370 
371  protected:
372  QgsAbstractFeatureIterator *mIter = nullptr;
373 
374 
375 };
376 
377 #ifndef SIP_RUN
378 
380  : mIter( iter )
381 {
382  if ( iter )
383  iter->ref();
384 }
385 
387  : mIter( fi.mIter )
388 {
389  if ( mIter )
390  mIter->ref();
391 }
392 
394 {
395  if ( mIter )
396  mIter->deref();
397 }
398 
400 {
401  return mIter ? mIter->nextFeature( f ) : false;
402 }
403 
405 {
406  if ( mIter )
407  mIter->mFetchedCount = 0;
408 
409  return mIter ? mIter->rewind() : false;
410 }
411 
413 {
414  if ( mIter )
415  mIter->mFetchedCount = 0;
416 
417  return mIter ? mIter->close() : false;
418 }
419 
420 inline bool QgsFeatureIterator::isClosed() const
421 {
422  return mIter ? mIter->mClosed && !mIter->mZombie : true;
423 }
424 
425 inline bool operator== ( const QgsFeatureIterator &fi1, const QgsFeatureIterator &fi2 )
426 {
427  return fi1.mIter == fi2.mIter;
428 }
429 
430 inline bool operator!= ( const QgsFeatureIterator &fi1, const QgsFeatureIterator &fi2 )
431 {
432  return !( fi1 == fi2 );
433 }
434 
435 inline void QgsFeatureIterator::setInterruptionChecker( QgsFeedback *interruptionChecker )
436 {
437  if ( mIter )
438  mIter->setInterruptionChecker( interruptionChecker );
439 }
440 
441 #endif
442 
443 #endif // QGSFEATUREITERATOR_H
Helper template that cares of two things: 1.
void iteratorClosed()
to be called by from subclass in close()
QgsAbstractFeatureIteratorFromSource(T *source, bool ownSource, const QgsFeatureRequest &request)
Internal feature iterator to be implemented within data providers.
virtual bool rewind()=0
reset the iterator to the starting position
RequestToSourceCrsResult
Possible results from the updateRequestToSourceCrs() method.
bool mZombie
A feature iterator may be closed already but still be serving features from the cache.
virtual void setInterruptionChecker(QgsFeedback *interruptionChecker)
Attach an object that can be queried regularly by the iterator to check if it must stopped.
virtual bool fetchFeature(QgsFeature &f)=0
If you write a feature iterator for your provider, this is the method you need to implement!...
virtual bool close()=0
end of iterating: free the resources / lock
long long mFetchedCount
Number of features already fetched by iterator.
CompileStatus
Status of expression compilation for filter expression requests.
@ PartiallyCompiled
Expression was partially compiled, but extra checks need to be applied to features.
@ Compiled
Expression was fully compiled and delegated to data provider source.
@ NoCompilation
Expression could not be compiled or not attempt was made to compile expression.
void deref()
Remove reference, delete if refs == 0.
virtual ~QgsAbstractFeatureIterator()=default
destructor makes sure that the iterator is closed properly
QgsFeatureRequest mRequest
A copy of the feature request.
CompileStatus compileStatus() const
Returns the status of expression compilation for filter expression requests.
virtual bool isValid() const
Returns if this iterator is valid.
virtual bool nextFeature(QgsFeature &f)
fetch next feature, return true on success
bool mClosed
Sets to true, as soon as the iterator is closed.
Class for doing transforms between two map coordinate systems.
Custom exception class for Coordinate Reference System related exceptions.
Definition: qgsexception.h:66
Wrapper for iterator of features from vector data provider or vector layer.
bool nextFeature(QgsFeature &f)
~QgsFeatureIterator()
Destructor deletes the iterator if it has no more references.
QgsAbstractFeatureIterator * mIter
bool isClosed() const
find out whether the iterator is still valid or closed already
void setInterruptionChecker(QgsFeedback *interruptionChecker)
Attach an object that can be queried regularly by the iterator to check if it must stopped.
bool compileFailed() const
Indicator if there was an error when sending the compiled query to the server.
QgsFeatureIterator()=default
Construct invalid iterator.
QgsAbstractFeatureIterator::CompileStatus compileStatus() const
Returns the status of expression compilation for filter expression requests.
This class wraps a request for features to a vector layer (or directly its vector data provider).
The feature class encapsulates a single feature including its unique ID, geometry and a list of field...
Definition: qgsfeature.h:56
Base class for feedback objects to be used for cancellation of something running in a worker thread.
Definition: qgsfeedback.h:45
A rectangle specified with double values.
Definition: qgsrectangle.h:42
This class contains information about how to simplify geometries fetched from a QgsFeatureIterator.
#define SIP_THROW(name)
Definition: qgis_sip.h:198
#define SIP_TYPEHINT(type)
Definition: qgis_sip.h:227
#define SIP_SKIP
Definition: qgis_sip.h:126
#define SIP_TRANSFER
Definition: qgis_sip.h:36
bool operator==(const QgsFeatureIterator &fi1, const QgsFeatureIterator &fi2)
bool operator!=(const QgsFeatureIterator &fi1, const QgsFeatureIterator &fi2)