NodeJS Callback Conventions and Your App
NodeJS has a pretty specific convention when implementing callbacks in modules - function(err,result). Does this always make sense?
Did It Work Or Didn't It?
I have a method on my Customer module where I add a customer to MongoDB:
But how do you structure your callback?
In some circles (like Backbone and jQuery) you use a success/fail approach - like I did above. You pass one callback in that fires if everything succeeds, another that fires if it fails. This convention is rather clean:
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Node's convention is a little different and (keeping in mind that I'm very new to Node) I can only guess that this convention came about to avoid deep nesting and excessively callback-heavy code. In Node, the style is thus:
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This code is clean and readable - and it's also less so that makes us happy. But in our method we have to do this... which is a bit wonky:
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Now if the save() method on newCustomer had followed the Node convention - then I could have just passed the callback directly into it:
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... which is almost certainly why this standard was adopted (and I like it!). But it doesn't so we have to write some extra code to handle it. And I could spend another few paragraphs musing on the goods and bads - but I don't know nearly enough to do such a thing, so let's move on...
What To Do?
If I learned anything from working with Rails over the last 6 years - it's to let Rails be Rails. This isn't a bad thing. Every time I try to get clever, I pay for it.
On the other hand, when I was talking to Batman yesterday (Dave Ward) he suggested the success/fail thing was a more widely-accepted way of doing things. Which I think I agree with... but the Node community doesn't. Thus my post.
Anyway - if the convention for NodeJS is to use callback(err,result) and I'm using NodeJS well - that's what I'll do. In fact I've already run into an interesting situation with Vows (the testing framework I talked about yesterday) where it expected that I was using this structure.
I'll have more to say about Vows in another post (I like it a lot) - but the fact that it (basically) wouldn't execute more than one callback nudged me into this entire discussion.I'd love to hear your thoughts.