Deconstructing the FT-991A CAT's Programmatic Interface
Fighting the 'god' Class

I have two programmatic interfaces for the FT-991A's CAT. There is no substantial complexity to the commands although some are overload. Rather than be a 'god' object the implementation acted as a container The container has public properties which act as subcontainers for related commands. Doing so eliminated the 'god' class but usability issues resulted.

Programmatically no command is published by more than one container. This was to respect the single responsibility principle. Deciding what went where was a chore because some commands could have been in multiple containers. In turn when trying to use the programmatic interface became a game of which subcontainer is the command in.

A second version was written with a 'god' class. The Interface defines 162 public methods and 75 events. The implementation is organized across 7 source files. The internal organization does not simplify the programmatic interface.

The simplification is sort of an inversion of control. A type can implement multiple interfaces and the interfaces describe the type's behavior. With a unavoidable 'god' class why not have it implement multiple 'unrelated' interfaces. This

                public class CatImplementation : ICat
can become
                public class CatImplementation : IVfo, IRxAudio, ...
Each interface will only expose related functionality such as VFO commands. A command can be exposed in multiple interfaces without violating the single responsibility principle as there is only one implementation.

The client view of the 'god' object limited to what the interface exposes

                IVfo vfo = new CatImplementation() as IVfo;
                vfo.VfoAFrequencyChanged += someEventHandler;
The approach above does have issues. Multiple instances of the CatImplementation would be a waste of resources. Besides that every instance has its own serial port. The approach to use would be to use dependency injection and declare the 'god' class as a singleton. Then register each interface with the singleton.

What Goes Where?

The CAT has 90 two-letter commands including the EX command. A number of the commands are overloaded but not to the extent of the EX command which has 153 overloads. A preliminary attempt has been made to organize the various interfaces. Currently the interfaces are :

InterfaceCommand Count
These interfaces only cover the 89 non-EX commands. There are probably some commands which will end up being added to other interfaces. Some interfaces may include EX command definitions. None of this is set in stone.