Thursday, February 16, 2006

Type Checking and Code Smells


I’ve been caught for a while in the endless debate between strongly typed languages, such as Java, and loosely typed languages, such as Python. The main question could roughly be reduced to “is strong type checking worth the price?”, for python supporters the answer is clearly “No!”, cause the java syntax burden is not bringing so much of a value. I usually am a strong supporter of a strong type checking (even if I never used smalltalk, for me everything is an object) but in most java projects I’ve seen, strong type checking was never enforced, so developers were just dealing with a heavier syntax without enjoying its benefits.

Testing can introduce some safety degrees at deployment and release time, ensuring some more confidence on the produced code, but in this way you’re supposed to introduce a full-featured test suite, to really confident on software stability in the long term. But type checking was really meant with another goal: bullet proof (or fool proof) design. The best design example I remember, was the 3,5” floppy: even if it approximately looked like a square, it was not; and there was only one way it could be inserted in the slot (unless you were really creative, of course…). I used this metaphor a lot of times when teaching Java and OOP, but I am starting to wonder if it’s any more valid.

I usually get extremely suspicious (and worried, if it’s a project I am working on) when I see two things in code: empty constructors (and a lot of setters) and a huge list of String attributes. These two smells often came along, so the resulting aroma is a perfect blend. Ok, one thing changed from some years ago: a good IDE now shows more and more information about attributes and parameters, so – sometimes – the pessimistic control offered by strong type checking, can be surrogated by an optimistic naming convention (after all developers are supposed not to be that stupid). Still this is not an argument that can save empty constructors (and the resulting partially instantiated objects) from being intrinsically evil, and I can’t believe that none of those String attributes is a potential class.

But to really get some benefit from a more OO refactoring of the code you need behaviour, and if you’re pushed between a presentation framework, which doesn’t enforce OO data, such as Struts, and a lazy coded DAO layer, there’s not so much behaviour left to add to your classes, so – like an old man that feels out of fashion – I would look at all those String attributes in the code, and feel intimately disgusted, but then instead of invoking a refactoring session I’d rather have a glass of wine, thinking that the old times were better…

An article on the Python vs Java debate by Bruce Eckel
Martin Fowler's code smell "Data Clump"

and ConstructorInitialization


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