Deserilialization of the objects

Objects stored in the XML file can be loaded back by using the function wxXmlSerializer::DeserializeFromXml(const wxString &file) where parameter file means the path to the input XML file. The function returns true value whether the objects was succesfully deserialized.

Next steps depends on that how the objects have been added to the serializer during their serialization. These different methods of access to the deserialized objects are described by the samples in this topic. All samples use the serializable class from the previous topic Creation of the serializable class.

Deserialization of the object stored as a root node

Objects stored in the XML file as the root node can be restored in two simple steps:

Restored data in serializable class can now be accessed via class members as can been seen in following example where the values will be loaded from this XML file:

<?xml version="1.0" encoding="utf-8"?>
<object owner="Example" version="1.0.0">
    <object_properties>
        <object type="SerializableObject">
            <property name="id" type="long">-1</property>
            <property name="wxStringProperty" type="string">Values loaded from XML file.</property>
            <property name="wxPointProperty" type="point">25,50</property>
            <property name="IntegerProperty" type="int">16</property>
        </object>
    </object_properties>
</object>

void PrintMembers(SerializableObject *obj)
{
    wxPrintf(obj->m_wxStringProperty << wxT("\n"));
    wxPrintf(wxT("%d, %d\n"), (obj->m_wxPointProperty).x, (obj->m_wxPointProperty).y);
    wxPrintf(wxT("%d\n\n"), obj->m_IntegerProperty);	
}

int main( int argc, char ** argv )
{
    // create the serializer
    wxXmlSerializer serializer;
	
    // initialize the serializer
    serializer.SetSerializerOwner(wxT("Example"));
    serializer.SetSerializerRootName(wxT("object"));
    serializer.SetSerializerVersion(wxT("1.0.0"));
	
    // create SerializableObject class instance with its default values
    SerializableObject *pObject= new SerializableObject();
	
    // print object's members with their default values
    wxPrintf(wxT("Data members of 'pObject' with their default values:\n"));
    PrintMembers(pObject);
	
    // add the object to the serializer as its root node
    serializer.SetRootItem(pObject);
		
    // load object's members values from XML file
    if(wxFileExists(wxT("data.xml")))
    {		
        serializer.DeserializeFromXml(wxT("data.xml"));
    }	
	
    // print object's members with values loaded from XML file
    wxPrintf(wxT("Data members of 'pObject' with values loaded from XML file:\n"));
    PrintMembers(pObject);
	
    wxPrintf(wxT("Press ENTER to exit...\n"));
    while(wxFgetc(stdin) != '\n');
}

For succesfull deserialization the serializer must be initialized to same values like in XML file.

Deseralization of objects arranged in a list and in the tree structure

After successful deserialization the stored class instances can be accessed by set of member functions declared in xsSerializable class:

Following example demonstrates how to restore and access a list of objects:

void PrintMembers(SerializableObject *obj)
{
    wxPrintf(obj->m_wxStringProperty << wxT("\n"));
    wxPrintf(wxT("%d, %d\n"), (obj->m_wxPointProperty).x, (obj->m_wxPointProperty).y);
    wxPrintf(wxT("%d\n\n"), obj->m_IntegerProperty);	
}

int main( int argc, char ** argv )
{
    // create the serializer
    wxXmlSerializer serializer;
			
    // load object's members values from XML file
    if(wxFileExists(wxT("data.xml")))
    {		
        serializer.DeserializeFromXml(wxT("data.xml"));
    }	
	
    // get pointer to the first serialized object
    SerializableObject *pObject = (SerializableObject*)serializer.GetRootItem()->GetFirstChild();
    while(pObject)
    {
        PrintMembers(pObject);
		
        // get next serialized object, pObject will be NULL if the object doesn't exist
        pObject = (SerializableObject*) ((xsSerializable*)pObject)->GetSibbling();
    }	
	
    wxPrintf(wxT("Press ENTER to exit...\n"));
    while(wxFgetc(stdin) != '\n');
}

An output of this sample application:

This modified sample demonstrates how to restore and access objects arranged in the tree structure: 

void PrintTree( xsSerializable *parent, int level )
{
    level++;
    wxString spaces = wxT("");
	
    // get the children of given parent
    SerializableObject *pObject = (SerializableObject*)parent->GetFirstChild();
	
    while( pObject )
    {
        // print info about data members of current object...
        for( int i = 1; i < level; i++ )
            spaces += wxT(" ");		
        wxPrintf(spaces);
        wxPrintf(pObject->m_wxStringProperty << wxT("\n"));
        wxPrintf(spaces);
        wxPrintf(wxT("%d, %d\n"), (pObject->m_wxPointProperty).x, (pObject->m_wxPointProperty).y);
        wxPrintf(spaces);
        wxPrintf(wxT("%d\n"), pObject->m_IntegerProperty);				
		
        // .. and process the object's children if exist
        if( pObject->HasChildren() ) PrintTree( pObject, level );
		
        // get sibbling of the current object
        pObject = (SerializableObject*)pObject->GetSibbling();
    }
}

int main( int argc, char ** argv )
{	
    // create instance of wxXmlSerializer
    wxXmlSerializer serializer;	
	
    // relooad stored objects from XML file
    serializer.DeserializeFromXml( wxT("data.xml") );	
	
    // print out info about loaded class instances
    PrintTree( serializer.GetRootItem(), 0 );		
	
    wxPrintf( wxT("\nPress ENTER to exit...\n") ); while( wxFgetc( stdin ) != '\n' );
}

In this sample the objects in a tree structure is browsed by recurently calling the function PrintTree.

An output of the application created from the source code above will look like this: