I think the biggest mistake with this post was approaching it from a “Hey, check out this interface” vs. “Hey, look at this sample code that uses it”.

I’m not saying that the method isn’t awkward. It’s a visitor pattern that just didn’t have a great place to go without introducing unnecessary complexity in achieving the goals we had.

That’s the thing — the “us” in FUBU seems to be a tight group.  The call to put a “WriteReport” in such a low-level interface, and from scratch (it was included in the first commit) seems so obtuse, and I’d be really surprised that there’s no backlash against that.  I’ve shown this interface to a few of my programming friends with a simple question “What is wrong here?” and everybody pointed at that method.   The same benefits could be had by putting it in another interface and tagging both on any implementing class.  

I don’t mean to make it a Ruby/C# thing, I’m just trying to point out that the thing being abstracted is, essentially, an object.  

Don’t worry, I won’t keep pestering you on this.  Have a good weekend!

IValueSource is the lowest level interface we have. We have APIs that sit on top of this ad make everything much more seemless.
Think about it more like this: you provide data and we do the magic. On top of that, we provide detailed diagnostics to answer the “what/who/how/why” of the entire process.I’m not going to split hairs with you on Ruby vs. .NET. Different strokes, man. If you’re in a static language and WANT to use it, then this lets you do exactly that.

This seems like a textbook “before” refactoring example, where the teacher gets the class to identify which part doesn’t fit.  The “after” is always to separate the two responsibilities into their own separate class.  But to knowingly mix these two, and at such a low-level thing like a “value source,” doesn’t seem that useful at all.  In all of the places that devs use “value sources” for settings, form post data, CSVs, or whatever, no one ever says “Ok, the work’s done, now it’s time to add a report.”

I’ve been doing Ruby full-time for a year or so.  Do you know what we call “the notion of a source of values?”  An object.

When push comes to shove, I think it’s OK to let that vision drive a design decision even if it’s a little on the awkward side (i.e., forcing you to implement a no-op).

It’s not something we take lightly. We obsess over those decisions for some time before biting the bullet.

There are a handful of generic/reusable implementations of IValueSource that take care of all the details for you and let you work with more primitive types (e.g., IDictionary).

throw new MethodNotImplementedException(); ?