Good design ghosts

April 24, 2006 by Artem

I can recall several cases, when a seemingly clean'n'simple class appeared to be a huge and difficult to debug entity with loads of underlying asynchronous logic. The simple and small public interface hides the implementation details and according to the good Object-Oriented style all the underlying details are private. Or is it a good style to hide the implementation details into many private methods?

As it often happens, the problem comes from a good idea overused to the extent, where it inhibits another good idea. The encapsulation makes it easy to use your classes or systems externally, but it should not make you forget the internal structure of the class. As Michael Feathers tells

It often means that there's some other abstraction hidden away inside the class that might be useful to pull out.

The class with a loads of private methods looks like a ghost of a good design over an old dirty dangerous grave. It is good to hide the internals of your system from the external clients, but don't forget about the next level and keep the sublevels clean as well.

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