16.4 - Multiple Inheritance and DtReaderWriter

While we normally avoid the use of multiple inheritance, several of the basic readable, writable types provided with VR-Forces (such as DtRwString) were created from existing classes by inheriting both DtReaderWriter and the existing class (DtString, for example, in the case of DtRwString).

Remember that if you cast an object constructed using multiple inheritance to a void * (for example, for inclusion on a VR-Link DtList) you must cast back to the original constructed type, not one of its ancestors. For example, the following will compile, but the result is undefined:

DtRwString * createString = new DtRwString("Test String");
void * tempVoid = createString;
... 

DtString * useString = (DtString *) tempVoid;
printf (useString->string());

For correct results, replace the last two lines with:

DtRwString * useString = (DtRwString *) tempVoid;
printf (useString->String());

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