COM Object Diagrams

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Because Visual Basic is deeply rooted in COM, and most samples that I've included are based on ActiveX projects, I occasionally provide a COM object diagram to further explain a sample application. COM objects are represented as rectangles with round edges. COM interfaces are illustrated as a line with a circle at one end (affectionately referred to as a lollipop). The noncircle end touches the rectangle. The de facto interface naming convention is to prefix an interface name with a capital letter "I." For an object to be considered a COM object, it must support the IUnknown interface. IUnknown is normally rooted at the top of the rectangle. (See Figure A-7.)

Figure A-7. COM object diagram.