From 98a1c233af2d5294854925ff03075c1e70f69331 Mon Sep 17 00:00:00 2001
From: Martin Dobias <wonder.sk@gmail.com>
Date: Tue, 9 Aug 2011 20:48:13 +0200
Subject: [PATCH] Added python bindings for QgsExpression

---
 python/core/core.sip          |  1 +
 python/core/qgsexpression.sip | 64 +++++++++++++++++++++++++++++++++++
 src/core/qgsexpression.h      |  5 ++-
 3 files changed, 69 insertions(+), 1 deletion(-)
 create mode 100644 python/core/qgsexpression.sip

diff --git a/python/core/core.sip b/python/core/core.sip
index 7a4b3563b7d..d775dfbfdd9 100644
--- a/python/core/core.sip
+++ b/python/core/core.sip
@@ -35,6 +35,7 @@
 %Include qgsdataprovider.sip
 %Include qgsdatasourceuri.sip
 %Include qgsdistancearea.sip
+%Include qgsexpression.sip
 %Include qgsfeature.sip
 %Include qgsfield.sip
 %Include qgsgeometry.sip
diff --git a/python/core/qgsexpression.sip b/python/core/qgsexpression.sip
new file mode 100644
index 00000000000..63539292c29
--- /dev/null
+++ b/python/core/qgsexpression.sip
@@ -0,0 +1,64 @@
+
+class QgsExpression
+{
+%TypeHeaderCode
+#include "qgsexpression.h"
+%End
+
+public:
+  QgsExpression( const QString& expr );
+  ~QgsExpression();
+
+  //! Returns true if an error occurred when parsing the input expression
+  bool hasParserError() const;
+  //! Returns parser error
+  QString parserErrorString() const;
+
+  //! Get the expression ready for evaluation - find out column indexes.
+  bool prepare( const QgsFieldMap& fields );
+
+  //! Get list of columns referenced by the expression
+  QStringList referencedColumns();
+  //! Returns true if the expression uses feature geometry for some computation
+  bool needsGeometry();
+
+  // evaluation
+
+  //! Evaluate the feature and return the result
+  //! @note prepare() should be called before calling this method
+  QVariant evaluate( QgsFeature* f = NULL );
+
+  //! Evaluate the feature and return the result
+  //! @note this method does not expect that prepare() has been called on this instance
+  QVariant evaluate( QgsFeature* f, const QgsFieldMap& fields );
+
+  //! Returns true if an error occurred when evaluating last input
+  bool hasEvalError() const;
+  //! Returns evaluation error
+  QString evalErrorString() const;
+  //! Set evaluation error (used internally by evaluation functions)
+  void setEvalErrorString( QString str );
+
+  //! Set the number for $rownum special column
+  void setCurrentRowNumber( int rowNumber );
+  //! Return the number used for $rownum special column
+  int currentRowNumber();
+
+  //! Return the parsed expression as a string - useful for debugging
+  QString dump() const;
+
+  //! Return calculator used for distance and area calculations
+  //! (used by internal functions)
+  QgsDistanceArea* geomCalculator();
+
+  //
+
+  // tells whether the identifier is a name of existing function
+  static bool isFunctionName( QString name );
+
+  // return index of the function in BuiltinFunctions array
+  static int functionIndex( QString name );
+
+  //! return quoted column reference (in double quotes)
+  static QString quotedColumnRef( QString name );
+};
diff --git a/src/core/qgsexpression.h b/src/core/qgsexpression.h
index 8f574288bf2..475e8479139 100644
--- a/src/core/qgsexpression.h
+++ b/src/core/qgsexpression.h
@@ -55,7 +55,7 @@ to find out indices of columns and then repeatedly call evaluate(feature).
 
 @note added in 2.0
 */
-class QgsExpression
+class CORE_EXPORT QgsExpression
 {
   public:
     QgsExpression( const QString& expr );
@@ -165,6 +165,9 @@ class QgsExpression
     // return index of the function in BuiltinFunctions array
     static int functionIndex( QString name );
 
+    //! return quoted column reference (in double quotes)
+    static QString quotedColumnRef( QString name ) { return QString( "\"%1\"" ).arg( name.replace( "\"", "\"\"" ) ); }
+
     //////
 
     class Node