Allow preparing expressions in QgsDataDefined without requiring a layer

nyalldawson · nyalldawson · commit 12f52690f318 · 2014-07-04T23:47:07.000+10:00
diff --git a/src/core/qgsdatadefined.cpp b/src/core/qgsdatadefined.cpp
@@ -65,7 +65,17 @@ bool QgsDataDefined::prepareExpression( QgsVectorLayer* layer )
     }
   }
 
-  mExpression->prepare( layer->pendingFields() );
+  if ( layer )
+  {
+    mExpression->prepare( layer->pendingFields() );
+  }
+  else
+  {
+    //preparing expression without a layer set, so pass empty field list
+    QgsFields empty;
+    mExpression->prepare( empty );
+  }
+
   if ( mExpression->hasEvalError() )
   {
     QgsDebugMsg( "Prepare error:" + mExpression->evalErrorString() );

Original file line number	Diff line number	Diff line change
`@@ -65,7 +65,17 @@ bool QgsDataDefined::prepareExpression( QgsVectorLayer* layer )`
`65`	`65`	`}`
`66`	`66`	`}`
`67`	`67`
`68`		`- mExpression->prepare( layer->pendingFields() );`
	`68`	`+ if ( layer )`
	`69`	`+ {`
	`70`	`+ mExpression->prepare( layer->pendingFields() );`
	`71`	`+ }`
	`72`	`+ else`
	`73`	`+ {`
	`74`	`+ //preparing expression without a layer set, so pass empty field list`
	`75`	`+ QgsFields empty;`
	`76`	`+ mExpression->prepare( empty );`
	`77`	`+ }`
	`78`	`+`
`69`	`79`	`if ( mExpression->hasEvalError() )`
`70`	`80`	`{`
`71`	`81`	`QgsDebugMsg( "Prepare error:" + mExpression->evalErrorString() );`