Saturday, July 26, 2014

The Wrong Abstraction

_I originally wrote the following for my Chainline Newsletter, but I continue to get tweets about this idea, so I'm re-publishing the article here on my blog. This version has been lightly edited._

I've been thinking about the consequences of the "wrong abstraction." My RailsConf 2014 "all the little things" talk included a section where I asserted:
duplication is far cheaper than the wrong abstraction
And in the summary, I went on to advise:
prefer duplication over the wrong abstraction
This small section of a much bigger talk invoked a surprisingly strong reaction. A few folks suggested that I had lost my mind, but many more expressed sentiments along the lines of:
“Duplication is far cheaper than the wrong abstraction.” @sandimetz @rbonales pic.twitter.com/zAmc9pvNS4
This, a million times this! “@BonzoESC: “Duplication is far cheaper than the wrong abstraction” @sandimetz @rbonales pic.twitter.com/3qMI0waqWb
View image on Twitter
The strength of the reaction made me realize just how widespread and intractable the "wrong abstraction" problem is. I started asking questions and came to see the following pattern:

  1. Programmer A sees duplication.
  2. Programmer A extracts duplication and gives it a name.
    This creates a new abstraction. It could be a new method, or perhaps even a new class.
  3. Programmer A replaces the duplication with the new abstraction.
    Ah, the code is perfect. Programmer A trots happily away.
  4. Time passes.
  5. A new requirement appears for which the current abstraction is almost perfect.
  6. Programmer B gets tasked to implement this requirement.
    Programmer B feels honor-bound to retain the existing abstraction, but since isn't exactly the same for every case, they alter the code to take a parameter, and then add logic to conditionally do the right thing based on the value of that parameter.
    What was once a universal abstraction now behaves differently for different cases.
  7. Another new requirement arrives.
    Programmer X.
    Another additional parameter.
    Another new conditional.
    Loop until code becomes incomprehensible.
  8. You appear in the story about here, and your life takes a dramatic turn for the worse.

No comments:

Post a Comment