Question

Never sure where to place functions like:

String PrettyPhone( String phoneNumber ) // return formatted [phone]
String EscapeInput( String inputString ) // gets rid of SQL-escapes like ' 

I create a Toolbox class for each application that serves as a repository for functions that don’t neatly fit into another class. I’ve read that such classes are bad programming practice, specifically bad Object Oriented Design. However, said references seem more the opinion of individual designers and developers more than an over-arching consensus. So my question is, Is a catch-all Toolbox a poor design pattern? If so, why, and what alternative is there?

Answer 1

Great question. I always find that any sufficiently complex project require “utility” classes. I think this is simply because the nature of object-oriented programming forces us to place things in a neatly structured hierarchical taxonomy, when this isn’t always feasible or appropriate (e.g. try creating an object model for mammals, and then squeeze the platypus in). This is the problem which motivates work into aspect oriented programming (c.f. cross cutting concern). Often what goes into a utility class are things that are cross-cutting concerns.

One alternative to using toolbox or utility classes, are to use extension methods to provide additional needed functionality to primitive types. However, the jury is still out on whether or not that constitutes good software design.

My final word on the subject is: go with it if you need, just make sure that you aren’t short-cutting better designs. Of course, you can always refactor later on if you need to.