Strongly Typed Primitives

No, I’m not talking about NEANDERTHALS (there’s a joke in there somewhere), but rather a technique that a colleague of mine, Josh Twist, has recently blogged about – “Avoiding Primitive Obsession to tip developers into the pit of success”. I’d always seen a pit as symbolic of failure, so I’m pretty pleased there’s such a thing as a pit of success – improves my odds massively J

I’ve drawn attention to this because it is an approach I discovered a few years back, and I love it. I just use a slightly different implementation to Josh;

public class Command

{

    #region Structure

    private string _name;

    private Command(string name)

    {

        _name = name;

    }

    public string Name

    {

        get

        {

            return _name;

        }

    }

    #endregion

    #region Instances

    public static Command Profile = new Command("Profile");

    public static Command WebExecute = new Command("WebExecute");

    #endregion

}

You can see that I use a single class to encapsulate both the behaviour of the Command class and the static instances of a Command.

I can’t really think of a convincing reason why one of these would be better over the other to be honest – I guess Josh’s approach means you could have different collections of commands (WebCommands, WindowsCommands, SomeOtherCommands), but I’ve never needed to do that. Any other reasons you can think of?

Still – read Josh’s post and see what you think. This kind of pattern is so simple yet so effective at eliminating mistypes, increasing code readability, and improving refactoring (just try deleting a command type and watch that compiler pick up everywhere you need to make a change!).

Good stuff.

Comments

• Anonymous
  August 15, 2008
  PingBack from http://informationsfunnywallpaper.cn/?p=740

• Anonymous
  August 15, 2008
  The comment has been removed

• Anonymous
  August 15, 2008
  @ Josh; I like it. In fact, come to think of it there are similarities to when I was building a navigation framework targeting both web and windows. I made a vague reference to this with my "Screen" class here; http://blogs.msdn.com/simonince/archive/2008/06/16/wcsf-application-architecture-4-environment-abstraction.aspx I forget exactly how it worked but I had to create different instances of the class because I wanted to use it to encapsulate information about how to actually navigate to a screen too - which obviously is very different in the web and windows worlds. Hmm. OK, so I think my approach is the version for beginners, yours is the posh one :-)

• Anonymous
  August 15, 2008
  You've been kicked (a good thing) - Trackback from DotNetKicks.com

• Anonymous
  August 15, 2008
  You can also make it generic so everything can fit in a small static class: public static class Command {    public static readonly Id<Command> Profile = (Id<Command>)"Profile";    public static readonly Id<Command> WebExecute = new (Id<Command>"WebExecute"; } Now the type name is just a marker so you can do everything with a single class, and just pick the best name (Command versus CommandName). I posted the code I use here: http://www.atrevido.net/blog/2008/08/15/Typing+String+IDs.aspx (Although, if you don't care about performance and nullability issues, a class-based inheritance system may provide more benefits.)

• Anonymous
  August 17, 2008
  The comment has been removed

• Anonymous
  August 18, 2008
  Ah, yes, keeping multiple items would be a pain right now. More reason to lean on the .NET teams to add tuples as first class citizens :).