Justin du Coeur (jducoeur) wrote,
Justin du Coeur
jducoeur

Dependencies, and the danger of import *

Just a quick thought for the programming crowd. I've spent most of this week focused on refactoring Querki -- it's needed it for a while, and the growing need to write some proper test harness is the straw that's breaking the camel's back. (Unit testing is always a good check of your factoring: poorly-factored code is usually hard to test.)

Along the way, I'm trying to clean up my dependencies, and I'm starting to realize how dangerous mass imports can really be. I have lots of places where I had quickly typed
import models._
or something like that. (Underscore is Scala's wildcard operator, pretty consistently, so think of that as "import models.*".)

It isn't so much that this automatically makes your code bad. (Although I am beginning to suspect that it is slowing down my compiles, by muddying the dependency tree.) But it promotes lazy thinking: these sorts of mass imports make it simply too easy to use a whole lot of different classes and traits, without thinking about the factoring implications. The result is classes that are often less cohesive than they should be, in no small part because it was slightly too easy to be that way.

So I'm gradually moving towards a coding standard of being more explicit about imports in most cases. Some packages and objects are specifically intended for wildcard import, and that's okay, but I'm coming to the conclusion that the rule of thumb should be usually not doing so.

I'm curious: what are your habits? Do you prefer wildcard imports or explicit ones?
Tags: programming
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