Thursday, June 30, 2011

Code generation is a basic developer skill

“Give a good developer a 40 hour task and he’ll spend 39 hours writing a program that can do the task in 1 hour.” – unknown

Really? This seems risky!

It can look risky, can’t it. You might end up with a half working program and not enough time to do the job. There are approaches that reduce this risk, but more on that later.

Why should you even bother? Simple math tells us it’s not faster to do so (at least not in the above example). However, experience tells us that in general most jobs will be repeated. Now, with the above example, if it’s only repeated once, you have a 39 hour profit, as you can now do the job in 1 hour.

Obviously, things don’t work like that in the real world. Automating a process usually takes longer than actually manually doing the work. In fact, when you want to automate something, that usually means you first have to do it by hand at least once, so you know what you’re automating.

But it’s also unlikely that you will only repeat a process just once. Often tasks are done many times and then it becomes worth the effort of automation. Let’s look at a current example.

A common case

As some of you may know, I’m working on a line of business application with a Silverlight UI and a WCF service layer (although the used technology doesn’t really matter for this case). Part of writing most line of business applications is writing business objects that represent your model and writing logic to retrieve data from the database, either directly or through some ORM.

Another part is writing lot’s of “forms” if you will, to input data into. Usually these forms follow a common pattern. Both of these parts, the business objects and the forms, contain a lot of repetitive work to do manually. Some of the code can be moved into generic super classes, but most of the code is of a nature that doesn’t allow for generalization. This is where automation comes into play. In this case, why write all that code yourself if you can also generate it?

When we first started out with this application, we did set out to build some code generation. Unfortunately most of us didn’t have a lot of experience with code generation as such, so wrong choices were made (C# generation with a StringBuilder is not the way to go and the same goes for Code DOM). After the initial versions of our code generation engine, we were forced to spend all our time on getting a first release out to our customers and no more work on automation in any form was a predictable result.

So, are you a good developer?

We all fall into this trap at some point. I know I have several times. You let a deadline pressure you to much, or you go back to your old na├»ve thinking saying that this will just be some demo code and it won’t end up in production anyway. Whatever the reason, we all end up breaking our own rules from time to time.

Don’t get me wrong, that doesn’t make you a bad developer. In fact it means you are focusing on how to providing value to your customers, which is key for a good developer. Also, breaking these rules from time to time keeps us alert on why they are rules in the first place.

However, we should also take time every now and then to take a step back and have a look at what we are doing. In my case I found we should put a lot more effort in making our development process more efficient. This means making more code generic, refactoring existing generic code to fit our needs better, and generating more code.

Generating code, a daunting task?

To some developers generating code may seem like a daunting task. Don’t worry. That’s a good thing, because you won’t just dive in without giving it some thought. As you can see from our example, having a developer that things “Oh, this is easy. I’ll just take a StringBuilder and push out lots of .cs files" is far from ideal.

Actually the first step in code generation is not writing a code generation process. It all starts with meta data. If you don’t have something to base your code generation process on, then how are you going to generate code in the first place?

In case of a line of business application, often your data model can provide you with some meta data. In fact we started out with a stored procedure that would take meta data from our data model in SQL Server and put it in another database. Then we would generate source from that data.

Another source for meta data may actually come from people entering that data into an application. We use that too, to allow our functional specialists to provide us with information to generate the forms in the GUI.

Once you have your meta data in some form or the other, you can write your generation process. Actually, that part doesn’t have to be hard. In the end it’s just creating text from data, which most web developers have been doing for years. The main problem is integrating your process with your IDE. That is where T4 comes in.

As some of you may know T4 is already used in Visual Studio to generate source code. It also provides you with a simple button to trigger the execution of all T4 templates within your solution. This is obviously a lot easier than adding files generated by some external program.

As for editing these templates, Visual Studio doesn’t come with standard support for this (it’s treated as text by default, so no IntelliSense). If you are serious about T4, you should check out Tangible. They have an editor for T4, integrated in Visual Studio, both in a free edition as well as a pro edition with more features. Both features do come with IntelliSense and Highlighting, but the free edition only supports limited namespaces and assemblies. You can find them here.

But what about those risks?

I hear you. Starting with this it can be scary. The trick is to start small and then keep on growing your code generation process to support more and more scenario’s. This way you can work on your code generation in iterations and have a working end result often. This reduces the risk, because you can, at any point, decide that you will no longer extend the code generation process, but extend the generated code by hand.

Also, before generating any code, you should have at least written and tested it once, to make sure you know the structure of your code and what meta data is needed in order to generate it. This way you also know you will end up with code that works.


I hope you realize the potential of code generation and how this can really make you more productive. I can tell you from experience that it also makes software development more fun, even if you have to build a lot of the same. With the right tools I’m confident that any development team could benefit from automating their work.