Classes, Debuggable Systems, and Web Components

Dave Thomas of The Pragmatic Programmer fame posted a few posts on class design in OO systems:

• Classless Can be Classy
• A Class with No State is Not a Class

He makes the case that if a routine requires no external state, it should not be part of a class. I guess?

The entire point of classes is to create objects in a way that not only encapsulates their state, but hides if they even have state in the first place.

SomeClass.new.some_method

You want to call some_method. In Ruby, you have to call that on some object. So you need that object. SomeClass.new gives you that object. If that object needs state or not, it doesn't matter and shouldn't. This is what you have to do to call the method.

Compare to:

SomeNamespace.some_method

Here, again, you want to call some_method which requires an object on which to call it. In this case, that object is the constant SomeNamespace. You didn't create it, and it may or may not have state. If it does, it's likely global, which is complicated and undesirable.

Behind the scenes, if some_method doesn't have state, I'd argue there's no real difference in these approaches, save for four characters: ., n, e, and w.

But creating some_method as a stateless function means if you need it to have state later…it's fairly difficult to achieve without requiring all callers to change.

I'm just not really sure what the benefit is supposed to be.

Some proponents of Dependency Injection believe you should never call .new (or new(...)). If that's how your system is designed, I would say again, none of this matters. Something somewhere is creating your objects for you. They are probably being created with .new and this is fine.

There's nothing wrong with making a class that currently has no state and has a no-arg constructor, and you will probably never regret designing your entire codebase that way.

Some Posts on My Blog

• It's important to create debuggable systems. To be honest, a simple architecture where you create classes with .new and call methods that have names is pretty darn debuggable.
• Adding a Confirmation Dialog You Can Style But Without Any JavaScript in BrutRB is a short screencast showing the power of Web Components and progressive enhancement. Stick around to the 8 minute mark to see some live electronic music, straight from a bunch of analog synthesizers.

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