CArchive::GetObjectSchema
Call this function from the Serialize function to determine the version of the object that is currently being deserialized.
UINT GetObjectSchema( );
Return Value
During deserialization, the version of the object being read.
Remarks
Calling this function is only valid when the CArchive object is being loaded (CArchive::IsLoading returns nonzero). It should be the first call in the Serialize function and called only once. A return value of (UINT)–1 indicates that the version number is unknown.
A CObject-derived class may use VERSIONABLE_SCHEMA combined (using bitwise OR) with the schema version itself (in the IMPLEMENT_SERIAL macro) to create a "versionable object," that is, an object whose Serialize member function can read multiple versions. The default framework functionality (without VERSIONABLE_SCHEMA) is to throw an exception when the version is mismatched.
Example
IMPLEMENT_SERIAL(CSchemaObject, CObject, VERSIONABLE_SCHEMA | 1)
void CSchemaObject::Serialize(CArchive& ar)
{
CObject::Serialize(ar);
if (ar.IsLoading())
{
int nVersion = ar.GetObjectSchema();
switch(nVersion)
{
case 0:
// read in previous version of
// this object
break;
case 1:
// read in current version of
// this object
break;
default:
// report unknown version of
// this object
break;
}
}
else
{
// Normal storing code goes here
}
}
Requirements
Header: afx.h