Base::Persistence Class Reference

#include <Base/Persistence.h>

Detailed Description

Persistence class and root of the type system.

Public Member Functions
virtual unsigned int	getMemSize (void) const =0
virtual void	Save (Writer &) const =0
virtual void	Restore (XMLReader &)=0
virtual void	SaveDocFile (Writer &) const
virtual void	RestoreDocFile (Reader &)
Public Member Functions inherited from Base::BaseClass
	BaseClass ()
	Construction.
virtual	~BaseClass ()
	Destruction.

Static Public Member Functions
static std::string	encodeAttribute (const std::string &)
	Encodes an attribute upon saving.

Member Function Documentation

getMemSize()

virtual unsigned int Base::Persistence::getMemSize ( void  ) const

pure virtual

This method is used to get the size of objects It is not meant to have the exact size, it is more or less an estimation which runs fast! Is it two bytes or a GB?

Implemented in App::Document, and App::Property.

Restore()

virtual void Base::Persistence::Restore ( XMLReader &  )

pure virtual

This method is used to restore properties from an XML document. It uses the XMLReader class, which bases on SAX, to read the in Save() written information. Again the Vector as an example:

void PropertyVector::Restore(Base::XMLReader &reader)
{
  // read my Element
  reader.readElement("PropertyVector");
  // get the value of my Attribute
  _cVec.x = reader.getAttributeAsFloat("valueX");
  _cVec.y = reader.getAttributeAsFloat("valueY");
  _cVec.z = reader.getAttributeAsFloat("valueZ");
}

Implemented in Gui::Document, App::TransactionObject, App::PropertyPythonObject, and App::Transaction.

RestoreDocFile()

virtual void Base::Persistence::RestoreDocFile ( Reader &  )

virtual

This method is used to restore large amounts of data from a file In this method you simply stream in your SaveDocFile() saved data. Again you have to apply for the call of this method in the Restore() call:

void PropertyMeshKernel::Restore(Base::XMLReader &reader)
{
  reader.readElement("Mesh");
  std::string file (reader.getAttribute("file") );

  if(file == "")
  {
    // read XML
    MeshCore::MeshDocXML restorer(*_pcMesh);
    restorer.Restore(reader);
  }else{
    // initiate a file read
    reader.addFile(file.c_str(),this);
 }
}

After you issued the reader.addFile() your RestoreDocFile() is called:

void PropertyMeshKernel::RestoreDocFile(Base::Reader &reader)
{
    _pcMesh->Read( reader );
}

See also

Base::Reader,Base::XMLReader

Reimplemented in Gui::Document.

Save()

virtual void Base::Persistence::Save ( Writer &  ) const

pure virtual

This method is used to save properties to an XML document. A good example you'll find in PropertyStandard.cpp, e.g. the vector:

void PropertyVector::Save (Writer &writer) const
{
   writer << writer.ind() << "<PropertyVector valueX=\"" <<  _cVec.x <<
                                          "\" valueY=\"" <<  _cVec.y <<
                                          "\" valueZ=\"" <<  _cVec.z <<"\"/>" << endl;
}

The writer.ind() expression writes the indentation, just for pretty printing of the XML. As you see, the writing of the XML document is not done with a DOM implementation because of performance reasons. Therefore the programmer has to take care that a valid XML document is written. This means closing tags and writing UTF-8.

See also

Base::Writer

Implemented in Gui::Document, and App::PropertyPythonObject.

SaveDocFile()

virtual void Base::Persistence::SaveDocFile ( Writer &  ) const

virtual

This method is used to save large amounts of data to a binary file. Sometimes it makes no sense to write property data as XML. In case the amount of data is too big or the data type has a more effective way to save itself. In this cases it is possible to write the data in a separate file inside the document archive. In case you want do so you have to re-implement SaveDocFile(). First, you have to inform the framework in Save() that you want do so. Here an example from the Mesh module which can save a (pontetionaly big) triangle mesh:

void PropertyMeshKernel::Save (Base::Writer &writer) const
{
  if (writer.isForceXML())
  {
    writer << writer.ind() << "<Mesh>" << std::endl;
    MeshCore::MeshDocXML saver(*_pcMesh);
    saver.Save(writer);
  }else{
   writer << writer.ind() << "<Mesh file=\"" << writer.addFile("MeshKernel.bms", this) << "\"/>" << std::endl;
}

The writer.isForceXML() is an indication to force you to write XML. Regardless of size and effectivness. The second part informs the Base::writer through writer.addFile("MeshKernel.bms", this) that this object wants to write a file with the given name. The method addFile() returns a unique name that then is written in the XML stream. This allows your RestoreDocFile() method to identify and read the file again. Later your SaveDocFile() method is called as many times as you issued the addFile() call:

void PropertyMeshKernel::SaveDocFile (Base::Writer &writer) const
{
    _pcMesh->Write( writer );
}

In this method you can simply stream your content to the file (Base::Writer inheriting from ostream).

Reimplemented in Gui::Document.