DaedTech

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Customizing Generated Method Header Comments

Editorial note: I originally wrote this post for the SubMain blog.  You can check out the original here, at their site.  While you’re there, have a look at GhostDoc, the subject of this post.

Last month, I wrote a post introducing you to T4 templates.  Near the end, I included a mention of GhostDoc’s use of T4 templates in automatically generating code comments.  Today, I’d like to expand on that.

To recap very briefly, recall that Ghost Doc allows you to generate things like method header comments.  I recommend that, in most cases, you let it do its thing.  It does a good job.  But sometimes, you might have occasion to want to tweak the result.  And you can do that by making use of T4 Templates.

Documenting Chess TDD

To demonstrate, let’s revisit my trusty toy code base, Chess TDD.  Because I put this code together for instructional purposes and not to release as a product, it has no method header comments for Intellisense’s benefit.  This makes it the perfect candidate for a demonstration.

If I had released this as a library, I’d have started the documentation with the Board class.  Most of the client interaction would happen via Board, so let’s document that.  It offers you a constructor and a bunch of semantics around placing and moving pieces.  Let’s document the conceptually simple “MovePiece” method.

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Intro to T4 Templates: Generating Text in a Hurry

Editorial Note: I originally wrote this post for the SubMain blog.  You can check out the original here, at their site.  While you’re there, take a look at GhostDoc.  In addition to comment generation capabilities, you can also effortlessly produce help documentation.

Today, I’d like to tackle a subject that inspires ambivalence in me.  Specifically, I mean the subject of automated text generation (including a common, specific flavor: code generation).

If you haven’t encountered this before, consider a common example.  When you file->new->(console) project, Visual Studio generates a Program.cs file.  This file contains standard includes, a program class, and a public static void method called “Main.”  Conceptually, you just triggered text (and code) generation.

Many schemes exist for doing this.  Really, you just need a templating scheme and some kind of processing engine to make it happen.  Think of ASP MVC, for instance.  You write markup sprinkled with interpreted variables (i.e. Razor), and your controller object processes that and spits out pure HTML to return as the response.  PHP and other server side scripting constructs operate this way and so do code/text generators.

However, I’d like to narrow the focus to a specific case: T4 templates.  You can use this powerful construct to generate all manner of text.  But use discretion, because you can also use this powerful construct to make a huge mess.  I wrote a post about the potential perils some years back, but suffice it to say that you should take care not to automate and speed up copy and paste programming.  Make sure your case for use makes sense.

The Very Basics

With the obligatory disclaimer out of the way, let’s get down to brass tacks.  I’ll offer a lightning fast getting started primer.

Open some kind of playpen project in Visual Studio, and add a new item.  You can find the item in question under the “General” heading as “Text Template.”

newtexttemplate

Give it a name.  For instance, I called mine “sample” while writing this post.  Once you do that, you will see it show up in the root directory of your project as Sample.tt.  Here is the text that it contains.

Save this file.  When you do so, Visual Studio will prompt you with a message about potentially harming your computer, so something must be happening behind the scenes, right?  Indeed, something has happened.  You have generated the output of the T4 generation process.  And you can see it by expanding the caret next to your Sample.tt file as shown here.

samplett

If you open the Sample.txt file, however, you will find it empty.  That’s because we haven’t done anything interesting yet.  Add a new line with the text “hello world” to the bottom of the Sample.tt file and then save.  (And feel free to get rid of that message about harming your computer by opting out, if you want).  You will now see a new Sample.txt file containing the words “hello world.”

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Generate Documentation from Your Build

Editorial Note: I originally wrote this post for the SubMain blog.  You can check out the original here, at their site.  While you’re there, have a look at GhostDoc.

Before I get down to the brass tacks of how to do some interesting stuff, I’m going to spin a tale of woe.  Well, I might have phrased that a little strongly.  Call it a tale of corporate drudgery.

In any case, many years ago I worked briefly in a little department, at a little company that seemed to be a corporate drudgery factory.  Oh, the place and people weren’t terrible.  But the work consisted of, well, drudgery.  We ‘consulted’ in the sense that we cranked out software for other companies, for pay.  Our software plumbed the lines of business between client CRMs and ERPs or whatever.  We would write the software, then finish the software, then hand the software over, source code and all.

Naturally, commenting our code and compliance with the coding standard attained crucial importance.  Why?  Well, no practical reason.  It was just that clients would see this code.  So it needed to look professional.  Or something.  Didn’t matter what the comments said.  Didn’t matter if the standard made sense.  Compliance earned you a gold star and a move onto the next project.

As I surveyed the scene surrounding me, I observed a mountain of vacuous comments and dirty, but uniform code.

My Complex Relationship with Code Comments

My brief stay with (and departure from) this organization coincided with my growing awareness of the Software Craftsmanship movement.  Even as they copy and pasted their way toward deadlines and wrote comments announcing that while(x < 6) would proceed while x was less than 6, I became interested in the idea of self-documenting code.

Up to that point, I had diligently commented each method, file, and type I encountered.  In this regard, I looked out for fellow and future programmers.  But after one too many occasions of watching my own comments turn into lies when someone changed the code without changing the comments, I gave up.  I stopped commenting my code, focusing entirely on extractions, refactoring, and making my code as legible as possible.

I achieved an equilibrium of sorts.  In this fashion, I did less work and stopped seeing my comments become nasty little fibs.  But a single, non-subtle flaw remained in this absolutist approach.  What about documentation of a public (or internal) API?

Naturally, I tried to apply the craftsmanship-oriented reasoning unilaterally.  Just make the public API so discoverable as to render the issue moot.  But that never totally satisfied me because I still liked my handy help screens and Intellisense info when consuming others’ code.

And so I came to view XML doc comments on public methods as an exception.  These, after all, did not represent “comments.”  They came packaged with your deliverables as your product.  And I remain comfortable with that take today.

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