MgSpatialContextReader Class Reference
[MgSpatialContextReader]

Provides forward-only, read-only functionality for enumerating spatial context information retrieved from a feature source. More...

Inherits MgSerializable.

List of all members.

Public Member Functions
void	Close ()
	Closes the SpatialContextReader object, freeing any resources it may be holding.
STRING	GetCoordinateSystem ()
STRING	GetCoordinateSystemWkt ()
STRING	GetDescription ()
MgByteReader *	GetExtent ()
INT32	GetExtentType ()
STRING	GetName ()
	Gets the name of the spatial context currently being read.
double	GetXYTolerance ()
double	GetZTolerance ()
bool	IsActive ()
bool	ReadNext ()
	Advances the reader to the next spatial context.
void	Reset ()
	Resets the SpatialContextReader object to the beginning just.

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Detailed Description

Provides forward-only, read-only functionality for enumerating spatial context information retrieved from a feature source.

Remarks:

You must call MgSpatialContextReader::ReadNext before you can access any data.

Example (PHP)

 <?php
 function printSpatialContextReader($spatialContextReader)
 {
    global $agfReaderWriter;
    global $logFileHandle;
    while ($spatialContextReader->ReadNext())
    {
       $name = $spatialContextReader->GetName();
       if ($name == NULL)
           $name = "null";

       fwrite($logFileHandle, "Spatial Context Name: "$name"n");
       $description = $spatialContextReader->GetDescription();
       if ($description == NULL)
           $description = "null";

       fwrite($logFileHandle, "Description: "$description"n");
       $coordSysName = $spatialContextReader->GetCoordinateSystem();
       if ($coordSysName == NULL)
           $coordSysName = "null";

       fwrite($logFileHandle, "Coordinate System Name: "$coordSysName"n");
       $coordSysWkt = $spatialContextReader->GetCoordinateSystemWkt();
       if ($coordSysWkt == NULL)
           $coordSysWkt = "null";

       fwrite($logFileHandle, "Coordinate System WKT: "$coordSysWkt"n");
       $extentType = $spatialContextReader->GetExtentType();
       fwrite($logFileHandle, "Extent Type: " . printExtentType($extentType) . "n");
       $extentByteReader = $spatialContextReader->GetExtent();
       if ($extentByteReader == NULL)
       {
          fwrite($logFileHandle, "MgSpatialContextReader::GetExtent() returned a NULL objectn");
       }
       else
       {
          $extentGeometry = $agfReaderWriter->Read($extentByteReader);
          printAGeometry($extentGeometry);
       }
       $XYTolerance = $spatialContextReader->GetXYTolerance();
       fwrite($logFileHandle, "XY Tolerance: $XYTolerancen");
       $ZTolerance = $spatialContextReader->GetZTolerance();
       fwrite($logFileHandle, "Z Tolerance: $ZTolerancen");
       $isActive = $spatialContextReader->IsActive();
       fwrite($logFileHandle, "Is Active: " . prtBool($isActive) . "n");
    }
 }
 ?>

Note:

See the FdoSpatialContextList XML schema for the specification of the contents of the information about a spatial context.

Example (C#)

The DescSpatialContexts method formats the contents of the MgSpatialContextReader as a string for testing purposes. The CoordSysWktToTypeAndName method extracts the coordinate system name and type from the well-known text specification of the coordinate system. The MgByteReaderToWktText method converts the geometry representing the extent of the spatial context from a binary to a textual format. The MgSpatialContextExtentTypeToStr method converts the extent type from an enumeration constant to a textual format.

 using OSGeo.MapGuide;
 private void DescSpatialContexts(MgSpatialContextReader reader)
 {
     String CoordSys;
     String CoordSysType;
     String CoordSysName;
     String OgcSrsWkt;
     String spatialContextInfo;
     String spatialContextName;
     MgByteReader byteReader;
     String Extent;
     testSpatialContexts = new ListDictionary();
     coordSysNameToWkt = new ListDictionary();
     while (reader.ReadNext())
     {
         CoordSys = reader.GetCoordinateSystem();
         OgcSrsWkt = reader.GetCoordinateSystemWkt();
         if (CoordSys == null)
         {
             CoordSys = "null";
         }
         else if (CoordSys == "")
         {
             CoordSys = "emptyString";
         }
         else if (CoordSys == OgcSrsWkt)
         {
             CoordSys = "duplicate of GetCoordinateSystemWkt()";
         }
         CoordSysWktToTypeAndName(OgcSrsWkt, out CoordSysType, out CoordSysName);
         coordSysNameToWkt.Add(CoordSysName, OgcSrsWkt);
         // byteReader contains FGF binary
         byteReader = reader.GetExtent();
         if (byteReader.GetLength() == 0)
         {
             Extent = "is empty";
         }
         else
         {
             Extent = MgByteReaderToWktText(byteReader);
         }
         spatialContextName = reader.GetName();
         spatialContextInfo = "SpatialContextName=" + spatialContextName + ';' +
             "GetCoordinateSystem()=" + CoordSys + ';' +
             "CoordSysType=" + CoordSysType + ';' +
             "CoordSysName=" + CoordSysName + ';' +
             "GetCoordinateSystemWkt()=" + OgcSrsWkt + ';' +
             "ExtentType=" + MgSpatialContextExtentTypeToStr(reader.GetExtentType()) + ';' +
             "Extent=" + Extent + ';' +
             "XYTolerance=" + reader.GetXYTolerance() + ';' +
             "ZTolerance=" + reader.GetZTolerance() + ';' +
             "Active=" + reader.IsActive() + ';';
         testSpatialContexts.Add(spatialContextName, spatialContextInfo);
     }
 }

 private String MgByteReaderToWktText(MgByteReader byteReader)
 {
     String wktText = null;
     MgGeometry geometry = agfReaderWriter.Read(byteReader);
     wktText = wktReaderWriter.Write(geometry);
     return wktText;
 }

 private void CoordSysWktToTypeAndName(String coordSysWkt,
     out String coordSysType, out String coordSysName)
 {
     String interim;
     String pattern = @"^([A-Z_]+)\[([^\,]+)";
     Regex r = new Regex(pattern);
     Match m = r.Match(coordSysWkt);
     GroupCollection gc = m.Groups;
     coordSysType = gc[1].Value;
     interim = gc[2].Value;
     coordSysName = interim.Trim('"');
 }

 String MgSpatialContextExtentTypeToStr(Int32 extentType)
 {
     switch (extentType)
     {
         case 0: return "Static";
         case 1: return "Dynamic";
         default: return "InvalidMgSpatialContextExtentType: " + extentType;
     }
 }

 private MgAgfReaderWriter agfReaderWriter;
 private MgWktReaderWriter wktReaderWriter;
 private MgSpatialContextReader spatialContextReader;
 private MgFeatureService featureService;
 private ListDictionary testSpatialContexts;
 private ListDictionary coordSysNameToWkt;

 agfReaderWriter = new MgAgfReaderWriter();
 wktReaderWriter = new MgWktReaderWriter();
 // see the MgFeatureService sample code
 spatialContextReader = featureService.GetSpatialContexts(resourceId, false);
 DescSpatialContexts(spatialContextReader);