Module Binder Pattern proposal

Whoa! This has been quite an event, the Directions EMEA 2016 in Prague. There has never been this many people (1.700+) and it was quite a pleasure connecting again with old friends, and meeting new friends. Also, it has been quite a pleasure listening to many good sessions, and an even bigger pleasure delivering four of them.

And this is why I am blogging now – to follow up on my promise during my Polymorphic Event Patterns for C/AL. I promised you that I’d post my pattern proposal online, and here I am doing it.

Let’s get started.

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From C/AL to executable: how NAV runs your C/AL code

A lot of folks write C/AL and never worry about what happens then. C/AL is written, NAV execute is, the story ends. The same way the story ends when you flush a toilet and the tank refills. How exactly? Who cares.

While understanding the inner workings of a toilet flush tank doesn’t necessarily make you more efficient at whatever it was that made you press the flush button in the first place, having a better understanding of exactly how NAV uses your C/AL code throughout its lifecycle is of arguably higher practical value.

Have you ever wondered what exactly happens to your C/AL code when you write it? How exactly does NAV run that stuff? Does it do any run-time interpretation, or does it compile C/AL into native code that runs on a processor? What does just-in-time compilation  mean and does it happen with C/AL? If so, when and why?

If any of these questions bother you, read on. If they don’t bother you, read on because they should bother you. If they don’t bother you because you know the answers, read on still, and then brag by poking holes in my explanation.

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I had a dream: codeunit references

Polymorphism is a great thing. .NET, Java, C++ and other folks have enjoyed its benefits for a long time, some more than a quarter century already. Meanwhile, we, the meager C/AL bunch, can only dream about it and draft our little patterns that all come short of it if only by a tiny bit.

Sometimes it feels like writing code with a chalk on a blackboard. There may be no end to your imagination, but there is a very real end to what the board can do for you.

But dream we can. And let me have another dream.

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Gentlemen’s agreement pattern, or handling the “Handled” pattern

I’ve delved deep into design patterns story with my last two blog posts, but I am far from over. The patterns I discussed are the ones we could use up until NAV 2015 (we can still use them, of course!) but some more robust loose coupling (excuse the near-oxymoron) can be achieved with what NAV 2016 brought along: events.

It’s the “Handled” pattern. This pattern comes from Thomas Hejlsberg, a chief architect and CTO of Microsoft Dynamics NAV, and was first described by Mark Brummel on his blog. It’s a powerful loose-coupling pattern that successfully addresses the shortcomings of all design patterns I discussed earlier. I would prefer calling this pattern Event Façade rather than “Handled”, but it’s not my baby to christen.

Let’s take a look.

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TempBlob Façade: a pattern proposition

Achieving some kind of polymorphism in C/AL has always been a problem. The fact that true polymorphism with pure C/AL is outright impossible has not stopped the more stubborn of us to at least give it a try. That’s how some cool patterns emerged.

The façade pattern has been evangelized by Gary Winter so eagerly that he couldn’t find time to formally describe it. The other pattern that comes close is the variant façade pattern. It was formally described at the patterns Wiki page, but – to the best of my knowledge – was first figured out by Arend-Jan Kauffmann.

These two patterns can go a long way. No, they are not coming anywhere near true polymorphism, but will achieve some cool loose binding when you need it.

In my practice, I took a step further, and I think it’s about time I share it. Let’s see if it works for you as well as it did for me.

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