19 - HELPER METHODS AVOID UNWANTED INHERITANCE

Summary

This column is really just an application of Composed Method to deal with inheritance. Now I always try to make my code fragments be real code, no As, Bs, and Cs. You can see why from the example here that is written the other way.

The column is interesting in that it contains some of the first explicit links between patterns. Down at the end it says, “Use Composed Method if necessary to set this pattern up.” I paid considerably more attention to pattern linking when I wrote the pattern book, and I'll probably pay a lot more attention with my next set of patterns.

Patterns in isolation are all very interesting, but it is when they are linked together that they become powerful. It is only then that you can explain a simple solution to a problem, because you know that the rest of the solution was handled by previous patterns or will be handled by future patterns.

The topic of this issue's column on Smalltalk idioms, following the general theme of inheritance, is how to manage the use of super. Several issues back I wrote a column entitled “The Dreaded Super,” in which I catalogued all the legitimate (and otherwise) uses of super in the existing Smalltalk/V and VisualWorks images. I'm still very proud of that column, but a couple of days ago I discovered I had left out one very important technique in dealing with super.