This topic pertains only to applications written in C++. DirectX for Visual Basic supports only loading of standard DirectMusic objects.

Specialized applications might create their own object types that encapsulate data from a file or resource. It can be convenient to have the DirectMusic loader handle the loading of such objects. This is especially true if the custom object is referred to by other objects or contains references to other objects.

To implement a loading mechanism that takes advantage of the DirectMusic loader, take the following steps:

• Register the object class so that it can be found by IDirectMusicLoader::GetObject.
• Implement the IDirectMusicObject interface on the object so that the loader can get the information that it needs to find and cache it.
• Implement the IPersistStream interface on the object, with full functionality in the IPersistStream::Load method. This allows you to parse the data that you obtain through calls on the IStream interface passed by the DirectMusicLoader.
• In the implementation of Load, ensure that references to other objects are dealt with by querying the IStream for the IDirectMusicGetLoader interface, then calling IDirectMusicGetLoader::GetLoader to obtain a pointer to the DirectMusicLoader that created the stream. Once you have this pointer, call IDirectMusicLoader::GetObject to load the new object.

An application might need to manage file input itself—for example, if all objects are stored in a special compressed resource file. The application can create its own loader by creating an object that supports the IDirectMusicLoader interface, with the IDirectMusicLoader::GetObject method implemented. All other methods are optional. This implementation of the loader must also create its own stream object that has both the IStream and the IDirectMusicGetLoader interfaces.