Default values - are they good or evil?
- by Andrew
The question about default values in general - default return function values, default parameter values, default logic for when something is missing, default logic for handling exceptions, default logic for handling the edge conditions etc.
For a long time I considered default values to be a "pure evil" thing, something that "cloaks the catastrophe" and results in a very hard do find bugs. But recently I started to think about default values as some sort of a technical debt ... which is not a straight bad thing but something that could provide some "short term financing" get us to survive the project (how many of us could afford to buy a house without taking out the mortgage?).
When I say a "short term" - I don't mean - "do something quickly first and do refactor it out later before it hits the production". No - I am talking about relying on a hardcoded default values in a production software. Granted - it could cause some issues, but what if it only going to cause a single trouble in a whole year.
Again - I am talking about the "average" mainstream software here (not a software for a nuclear power station) - the average web site or a UI application for the accounting software, meaning that people lives are not at stake, nor millions of dollars.
Again, from my experience, business users would rather live with the software which "works somehow", rather then wait for a perfect one. And the use of default values helps a lot if you develop a software in a RAD style. But again - the longest debug sessions I have spent were because of the bugs introduced by a default value which either stopped being "a default" along the way or because a small subsystem has recently been upgraded and as a result of this upgrade it does not handle the default correctly (e.g. empty list vs null, or null string vs empty string).
So my question is - are the default values good or evil. And if they are a technical debt - how do measure up how much you can borrow so you can afford the repayments?
Would really appreciate any input.
Cheers.
EDIT:
If I am using the default values as a way to cut the corners during the development - and if the corners cutting results in a bugs and issues - what is the methodology to recover from these issues?
