Re^2: Skipping the middle man & the SUPER gotcha

Seconded.

There's also another very important rule that I got from "Smalltalk Best Practice Patterns" (by Kent Beck) (I believe), which should be required reading for anyone doing serious OO. Yeah, it's all about Smalltalk, but most of the rules apply to any late-binding OO language like Perl.

The rule is that superclass calls should be made only to the same-named method. In other words, if you're in foo, you should never be calling SUPER::bar. This is the sign of a misunderstanding about SUPER and about objects in general. The point of SUPER is to extend a parent class behavior, not mix it up.

Wanting to "call the code two levels up" or "call a method other than your own name" are both signs of muddled thinking or an extremely bad class design.

-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

Comment on Re^2: Skipping the middle man & the SUPER gotcha

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Re^3: Skipping the middle man & the SUPER gotcha by tlm (Prior) on Apr 02, 2005 at 18:31 UTC
Thanks for the ref to the Beck book. Yeah, it's all about Smalltalk, but most of the rules apply to any late-binding OO language like Perl. Could you or some other knowledgeable monk clue me in about this business of "late-binding"? I googled the definition, but I'm having a much harder time finding some bird's-eye picture of the fundamental qualitative differences between OO languages that are late-binding and those that aren't. I vaguely gather that early-binding may be tied to strong typing, but this is just a guess. Wanting to "call the code two levels up" or "call a method other than your own name" are both signs of muddled thinking or an extremely bad class design. Yes, agreed, and I don't recall ever needing to do this in classes I have coded, but unfortunately one often has to work with class hierarchies designed by others. In fact, what motivated this meditation was a practical problem posted in SoPW; one simple solution to that problem amounted to "skipping the middle man". Without knowing much of the OO theory behind it, I've figured that the ability to "skip the middleman" is, like the `goto LABEL` facility, something to use sparingly, but nice to have available for the once in a blue moon when you really need it (otherwise Perl would have simply disallowed it). But in light of your and adrianh's comments, I regret having made the whole maneuver sound as innocuous as I did. the lowliest monk	[reply] [d/l]
Re^4: Skipping the middle man & the SUPER gotcha by merlyn (Sage) on Apr 02, 2005 at 18:36 UTC
Late binding means that variables aren't typed—values are. Perl, ruby, Smalltalk, and python are all examples of late-binding OO languages. C++ and Java are not. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply]
Re^3: Skipping the middle man & the SUPER gotcha by adrianh (Chancellor) on Apr 02, 2005 at 16:33 UTC
There's also another very important rule that I got from "Smalltalk Best Practice Patterns" (by Kent Beck) (I believe), which should be required reading for anyone doing serious OO. Totally agree. One of my favourite books. (and everybody should have to learn Smalltalk once in their life anyway :-)	[reply]