QgsVectorFileWriter: add capability to export displayed values of fie…

…lds (typically coming from edit widgets) instead of their raw values
qgis · May 14, 2016 · 038b3b7 · 038b3b7
1 parent b38a16f
commit 038b3b7
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Showing 4 changed files with 252 additions and 23 deletions.
diff --git a/python/core/qgsvectorfilewriter.sip b/python/core/qgsvectorfilewriter.sip
@@ -1,11 +1,8 @@
 /** \ingroup core
   * A convenience class for writing vector files to disk.
  There are two possibilities how to use this class:
- 1. static call to QgsVectorFileWriter::writeAsShapefile(...) which saves the whole vector layer
+ 1. static call to QgsVectorFileWriter::writeAsVectorFormat(...) which saves the whole vector layer
  2. create an instance of the class and issue calls to addFeature(...)
-
- Currently supports only writing to shapefiles, but shouldn't be a problem to add capability
- to support other OGR-writable formats.
  */
 class QgsVectorFileWriter
 {
@@ -107,6 +104,32 @@ class QgsVectorFileWriter
       SymbolLayerSymbology //Exports one feature per symbol layer (considering symbol levels)
     };
 
+    /** Interface to convert raw field values to their user-friendly value.
+     * @note Added in QGIS 2.16
+     */
+    class FieldValueConverter
+    {
+      public:
+        /** Constructor */
+        FieldValueConverter();
+
+        /** Destructor */
+        virtual ~FieldValueConverter();
+
+        /** Return a possibly modified field definition. Default implementation will return provided field unmodified.
+         * @param field original field definition
+         * @return possibly modified field definition
+         */
+        virtual QgsField fieldDefinition( const QgsField& field );
+
+        /** Convert the provided value, for field fieldIdxInLayer. Default implementation will return provided value unmodified.
+         * @param fieldIdxInLayer field index
+         * @param value original raw value
+         * @return possibly modified value.
+         */
+        virtual QVariant convert( int fieldIdxInLayer, const QVariant& value );
+    };
+
     /** Write contents of vector layer to an (OGR supported) vector formt
      * @param layer layer to write
      * @param fileName file name to write to
@@ -127,6 +150,7 @@ class QgsVectorFileWriter
      * @param forceMulti set to true to force creation of multi* geometries (added in QGIS 2.14)
      * @param includeZ set to true to include z dimension in output. This option is only valid if overrideGeometryType is set. (added in QGIS 2.14)
      * @param attributes attributes to export (empty means all unless skipAttributeCreation is set)
+     * @param fieldValueConverter field value converter (added in QGIS 2.16)
      */
     static WriterError writeAsVectorFormat( QgsVectorLayer* layer,
                                             const QString& fileName,
@@ -145,7 +169,8 @@ class QgsVectorFileWriter
                                             QgsWKBTypes::Type overrideGeometryType = QgsWKBTypes::Unknown,
                                             bool forceMulti = false,
                                             bool includeZ = false,
-                                            QgsAttributeList attributes = QgsAttributeList()
+                                            QgsAttributeList attributes = QgsAttributeList(),
+                                            FieldValueConverter* fieldValueConverter = nullptr
                                           );
 
     /** Writes a layer out to a vector file.
@@ -168,6 +193,7 @@ class QgsVectorFileWriter
      * @param forceMulti set to true to force creation of multi* geometries (added in QGIS 2.14)
      * @param includeZ set to true to include z dimension in output. This option is only valid if overrideGeometryType is set. (added in QGIS 2.14)
      * @param attributes attributes to export (empty means all unless skipAttributeCreation is set)
+     * @param fieldValueConverter field value converter (added in QGIS 2.16)
      * @note added in 2.2
      */
     static WriterError writeAsVectorFormat( QgsVectorLayer* layer,
@@ -187,7 +213,8 @@ class QgsVectorFileWriter
                                             QgsWKBTypes::Type overrideGeometryType = QgsWKBTypes::Unknown,
                                             bool forceMulti = false,
                                             bool includeZ = false,
-                                            QgsAttributeList attributes = QgsAttributeList()
+                                            QgsAttributeList attributes = QgsAttributeList(),
+                                            FieldValueConverter* fieldValueConverter = nullptr
                                           );
 
     /** Create a new vector file writer */

diff --git a/src/core/qgsvectorfilewriter.cpp b/src/core/qgsvectorfilewriter.cpp
@@ -52,6 +52,23 @@
 #define TO8F(x)  QFile::encodeName( x ).constData()
 #endif
 
+QgsVectorFileWriter::FieldValueConverter::FieldValueConverter()
+{
+}
+
+QgsVectorFileWriter::FieldValueConverter::~FieldValueConverter()
+{
+}
+
+QgsField QgsVectorFileWriter::FieldValueConverter::fieldDefinition( const QgsField& field )
+{
+  return field;
+}
+
+QVariant QgsVectorFileWriter::FieldValueConverter::convert( int /*fieldIdxInLayer*/, const QVariant& value )
+{
+  return value;
+}
 
 QgsVectorFileWriter::QgsVectorFileWriter(
   const QString &theVectorFileName,
@@ -74,8 +91,10 @@ QgsVectorFileWriter::QgsVectorFileWriter(
     , mWkbType( QGis::fromOldWkbType( geometryType ) )
     , mSymbologyExport( symbologyExport )
     , mSymbologyScaleDenominator( 1.0 )
+    , mFieldValueConverter( nullptr )
 {
-  init( theVectorFileName, theFileEncoding, fields, QGis::fromOldWkbType( geometryType ), srs, driverName, datasourceOptions, layerOptions, newFilename );
+  init( theVectorFileName, theFileEncoding, fields, QGis::fromOldWkbType( geometryType ),
+        srs, driverName, datasourceOptions, layerOptions, newFilename, nullptr );
 }
 
 QgsVectorFileWriter::QgsVectorFileWriter( const QString& vectorFileName, const QString& fileEncoding, const QgsFields& fields, QgsWKBTypes::Type geometryType, const QgsCoordinateReferenceSystem* srs, const QString& driverName, const QStringList& datasourceOptions, const QStringList& layerOptions, QString* newFilename, QgsVectorFileWriter::SymbologyExport symbologyExport )
@@ -88,11 +107,48 @@ QgsVectorFileWriter::QgsVectorFileWriter( const QString& vectorFileName, const Q
     , mWkbType( geometryType )
     , mSymbologyExport( symbologyExport )
     , mSymbologyScaleDenominator( 1.0 )
+    , mFieldValueConverter( nullptr )
+{
+  init( vectorFileName, fileEncoding, fields, geometryType, srs, driverName,
+        datasourceOptions, layerOptions, newFilename, nullptr );
+}
+
+QgsVectorFileWriter::QgsVectorFileWriter( const QString& vectorFileName,
+    const QString& fileEncoding,
+    const QgsFields& fields,
+    QgsWKBTypes::Type geometryType,
+    const QgsCoordinateReferenceSystem* srs,
+    const QString& driverName,
+    const QStringList& datasourceOptions,
+    const QStringList& layerOptions,
+    QString* newFilename,
+    QgsVectorFileWriter::SymbologyExport symbologyExport,
+    FieldValueConverter* fieldValueConverter )
+    : mDS( nullptr )
+    , mLayer( nullptr )
+    , mOgrRef( nullptr )
+    , mGeom( nullptr )
+    , mError( NoError )
+    , mCodec( nullptr )
+    , mWkbType( geometryType )
+    , mSymbologyExport( symbologyExport )
+    , mSymbologyScaleDenominator( 1.0 )
+    , mFieldValueConverter( nullptr )
 {
-  init( vectorFileName, fileEncoding, fields, geometryType, srs, driverName, datasourceOptions, layerOptions, newFilename );
+  init( vectorFileName, fileEncoding, fields, geometryType, srs, driverName,
+        datasourceOptions, layerOptions, newFilename, fieldValueConverter );
 }
 
-void QgsVectorFileWriter::init( QString vectorFileName, QString fileEncoding, const QgsFields& fields, QgsWKBTypes::Type geometryType, const QgsCoordinateReferenceSystem* srs, const QString& driverName, QStringList datasourceOptions, QStringList layerOptions, QString* newFilename )
+void QgsVectorFileWriter::init( QString vectorFileName,
+                                QString fileEncoding,
+                                const QgsFields& fields,
+                                QgsWKBTypes::Type geometryType,
+                                const QgsCoordinateReferenceSystem* srs,
+                                const QString& driverName,
+                                QStringList datasourceOptions,
+                                QStringList layerOptions,
+                                QString* newFilename,
+                                FieldValueConverter* fieldValueConverter )
 {
   mRenderContext.setRendererScale( mSymbologyScaleDenominator );
 
@@ -350,11 +406,19 @@ void QgsVectorFileWriter::init( QString vectorFileName, QString fileEncoding, co
   mAttrIdxToOgrIdx.clear();
   QSet<int> existingIdxs;
 
+  mFieldValueConverter = fieldValueConverter;
+
   for ( int fldIdx = 0; fldIdx < fields.count(); ++fldIdx )
   {
-    const QgsField& attrField = fields[fldIdx];
+    QgsField attrField = fields[fldIdx];
 
     OGRFieldType ogrType = OFTString; //default to string
+
+    if ( fieldValueConverter )
+    {
+      attrField = fieldValueConverter->fieldDefinition( fields[fldIdx] );
+    }
+
     int ogrWidth = attrField.length();
     int ogrPrecision = attrField.precision();
     if ( ogrPrecision > 0 )
@@ -1806,11 +1870,16 @@ OGRFeatureH QgsVectorFileWriter::createFeature( QgsFeature& feature )
     int fldIdx = it.key();
     int ogrField = it.value();
 
-    const QVariant& attrValue = feature.attribute( fldIdx );
+    QVariant attrValue = feature.attribute( fldIdx );
 
     if ( !attrValue.isValid() || attrValue.isNull() )
       continue;
 
+    if ( mFieldValueConverter )
+    {
+      attrValue = mFieldValueConverter->convert( fldIdx, attrValue );
+    }
+
     switch ( attrValue.type() )
     {
 #if defined(GDAL_VERSION_NUM) && GDAL_VERSION_NUM >= 2000000
@@ -2047,7 +2116,8 @@ QgsVectorFileWriter::writeAsVectorFormat( QgsVectorLayer* layer,
     QgsWKBTypes::Type overrideGeometryType,
     bool forceMulti,
     bool includeZ,
-    QgsAttributeList attributes )
+    QgsAttributeList attributes,
+    FieldValueConverter* fieldValueConverter )
 {
   QgsCoordinateTransform* ct = nullptr;
   if ( destCRS && layer )
@@ -2056,7 +2126,10 @@ QgsVectorFileWriter::writeAsVectorFormat( QgsVectorLayer* layer,
   }
 
   QgsVectorFileWriter::WriterError error = writeAsVectorFormat( layer, fileName, fileEncoding, ct, driverName, onlySelected,
-      errorMessage, datasourceOptions, layerOptions, skipAttributeCreation, newFilename, symbologyExport, symbologyScale, filterExtent, overrideGeometryType, forceMulti, includeZ, attributes );
+      errorMessage, datasourceOptions, layerOptions, skipAttributeCreation,
+      newFilename, symbologyExport, symbologyScale, filterExtent,
+      overrideGeometryType, forceMulti, includeZ, attributes,
+      fieldValueConverter );
   delete ct;
   return error;
 }
@@ -2078,7 +2151,8 @@ QgsVectorFileWriter::WriterError QgsVectorFileWriter::writeAsVectorFormat( QgsVe
     QgsWKBTypes::Type overrideGeometryType,
     bool forceMulti,
     bool includeZ,
-    QgsAttributeList attributes )
+    QgsAttributeList attributes,
+    FieldValueConverter* fieldValueConverter )
 {
   if ( !layer )
   {
@@ -2183,10 +2257,12 @@ QgsVectorFileWriter::WriterError QgsVectorFileWriter::writeAsVectorFormat( QgsVe
   }
 
   QgsVectorFileWriter* writer =
-    new QgsVectorFileWriter( fileName, fileEncoding, fields, QGis::fromNewWkbType( destWkbType ), outputCRS, driverName, datasourceOptions, layerOptions, newFilename, symbologyExport );
+    new QgsVectorFileWriter( fileName, fileEncoding, fields, destWkbType,
+                             outputCRS, driverName, datasourceOptions, layerOptions,
+                             newFilename, symbologyExport,
+                             fieldValueConverter );
   writer->setSymbologyScaleDenominator( symbologyScale );
 
-
   if ( newFilename )
   {
     QgsDebugMsg( "newFilename = " + *newFilename );
@@ -2261,6 +2337,8 @@ QgsVectorFileWriter::WriterError QgsVectorFileWriter::writeAsVectorFormat( QgsVe
   }
 
   writer->resetMap( attributes );
+  // Reset mFields to layer fields, and not just exported fields
+  writer->mFields = layer->fields();
 
   // write all features
   while ( fit.nextFeature( fet ) )

diff --git a/src/core/qgsvectorfilewriter.h b/src/core/qgsvectorfilewriter.h
@@ -33,11 +33,8 @@ class QTextCodec;
 /** \ingroup core
   * A convenience class for writing vector files to disk.
  There are two possibilities how to use this class:
- 1. static call to QgsVectorFileWriter::writeAsShapefile(...) which saves the whole vector layer
+ 1. static call to QgsVectorFileWriter::writeAsVectorFormat(...) which saves the whole vector layer
  2. create an instance of the class and issue calls to addFeature(...)
-
- Currently supports only writing to shapefiles, but shouldn't be a problem to add capability
- to support other OGR-writable formats.
  */
 class CORE_EXPORT QgsVectorFileWriter
 {
@@ -160,6 +157,32 @@ class CORE_EXPORT QgsVectorFileWriter
       SymbolLayerSymbology //Exports one feature per symbol layer (considering symbol levels)
     };
 
+    /** Interface to convert raw field values to their user-friendly value.
+     * @note Added in QGIS 2.16
+     */
+    class FieldValueConverter
+    {
+      public:
+        /** Constructor */
+        FieldValueConverter();
+
+        /** Destructor */
+        virtual ~FieldValueConverter();
+
+        /** Return a possibly modified field definition. Default implementation will return provided field unmodified.
+         * @param field original field definition
+         * @return possibly modified field definition
+         */
+        virtual QgsField fieldDefinition( const QgsField& field );
+
+        /** Convert the provided value, for field fieldIdxInLayer. Default implementation will return provided value unmodified.
+         * @param fieldIdxInLayer field index
+         * @param value original raw value
+         * @return possibly modified value.
+         */
+        virtual QVariant convert( int fieldIdxInLayer, const QVariant& value );
+    };
+
     /** Write contents of vector layer to an (OGR supported) vector formt
      * @param layer layer to write
      * @param fileName file name to write to
@@ -180,6 +203,7 @@ class CORE_EXPORT QgsVectorFileWriter
      * @param forceMulti set to true to force creation of multi* geometries (added in QGIS 2.14)
      * @param includeZ set to true to include z dimension in output. This option is only valid if overrideGeometryType is set. (added in QGIS 2.14)
      * @param attributes attributes to export (empty means all unless skipAttributeCreation is set)
+     * @param fieldValueConverter field value converter (added in QGIS 2.16)
      */
     static WriterError writeAsVectorFormat( QgsVectorLayer* layer,
                                             const QString& fileName,
@@ -198,7 +222,8 @@ class CORE_EXPORT QgsVectorFileWriter
                                             QgsWKBTypes::Type overrideGeometryType = QgsWKBTypes::Unknown,
                                             bool forceMulti = false,
                                             bool includeZ = false,
-                                            QgsAttributeList attributes = QgsAttributeList()
+                                            QgsAttributeList attributes = QgsAttributeList(),
+                                            FieldValueConverter* fieldValueConverter = nullptr
                                           );
 
     /** Writes a layer out to a vector file.
@@ -221,6 +246,7 @@ class CORE_EXPORT QgsVectorFileWriter
      * @param forceMulti set to true to force creation of multi* geometries (added in QGIS 2.14)
      * @param includeZ set to true to include z dimension in output. This option is only valid if overrideGeometryType is set. (added in QGIS 2.14)
      * @param attributes attributes to export (empty means all unless skipAttributeCreation is set)
+     * @param fieldValueConverter field value converter (added in QGIS 2.16)
      * @note added in 2.2
      */
     static WriterError writeAsVectorFormat( QgsVectorLayer* layer,
@@ -240,7 +266,8 @@ class CORE_EXPORT QgsVectorFileWriter
                                             QgsWKBTypes::Type overrideGeometryType = QgsWKBTypes::Unknown,
                                             bool forceMulti = false,
                                             bool includeZ = false,
-                                            QgsAttributeList attributes = QgsAttributeList()
+                                            QgsAttributeList attributes = QgsAttributeList(),
+                                            FieldValueConverter* fieldValueConverter = nullptr
                                           );
 
     /** Create a new vector file writer */
@@ -358,8 +385,42 @@ class CORE_EXPORT QgsVectorFileWriter
 
     QString mOgrDriverName;
 
+    /** Field value converter */
+    FieldValueConverter* mFieldValueConverter;
+
   private:
-    void init( QString vectorFileName, QString fileEncoding, const QgsFields& fields, QgsWKBTypes::Type geometryType, const QgsCoordinateReferenceSystem* srs, const QString& driverName, QStringList datasourceOptions, QStringList layerOptions, QString* newFilename );
+
+    /** Create a new vector file writer.
+     * @param vectorFileName file name to write to
+     * @param fileEncoding encoding to use
+     * @param fields fields to write
+     * @param geometryType geometry type of output file
+     * @param srs spatial reference system of output file
+     * @param driverName OGR driver to use
+     * @param datasourceOptions list of OGR data source creation options
+     * @param layerOptions list of OGR layer creation options
+     * @param newFilename potentially modified file name (output parameter)
+     * @param symbologyExport symbology to export
+     * @param fieldValueConverter field value converter (added in QGIS 2.16)
+     */
+    QgsVectorFileWriter( const QString& vectorFileName,
+                         const QString& fileEncoding,
+                         const QgsFields& fields,
+                         QgsWKBTypes::Type geometryType,
+                         const QgsCoordinateReferenceSystem* srs,
+                         const QString& driverName,
+                         const QStringList &datasourceOptions,
+                         const QStringList &layerOptions,
+                         QString *newFilename,
+                         SymbologyExport symbologyExport,
+                         FieldValueConverter* fieldValueConverter
+                       );
+
+    void init( QString vectorFileName, QString fileEncoding, const QgsFields& fields,
+               QgsWKBTypes::Type geometryType, const QgsCoordinateReferenceSystem* srs,
+               const QString& driverName, QStringList datasourceOptions,
+               QStringList layerOptions, QString* newFilename,
+               FieldValueConverter* fieldValueConverter );
     void resetMap( const QgsAttributeList &attributes );
 
     QgsRenderContext mRenderContext;