Why engines and components are not evil but distracting

I’ve been following the enthusiasm for engines, components, and bigger plugins from the sidelines for a while now. It’s a subject of very mixed emotions. On the one hand, I’m really glad to see that people get so excited and start dreaming of bigger and better things. That’s passion in the works and its great.

On the other hand, I think these developments are basically another name for high-level components. And you all know how I feel about those. The short summary is that high-level components are a mirage: By the time they become interesting, their fitting will require more work than creating something from scratch.

But I start getting really high eyebrows when I hear of “engines that depend on other engines that can be swapped out with yet another engine”. Even plugin dependencies are dangerously close to something I would consider unfit for Rails. Simply because it encourages a style of development that I find unhealthy.

So this is not a slam against the technical merits or implementation of either engines or anything else in the same boat. It’s a concern that they will distract people, that they will appear as needed, and in turn, that they will take the debacle that was Salted Hash Login to a new standardized level.

Rails is all about making the simple things so easy that you need not abstract them. It’s about making the creation of logins, of access control, of content management, of all these business logic components so very easy that you will treasure the application-specific solutions of your own rather than long for The One True Login System.

So what am I saying? That engines should be stopped? Of course not. But I am saying that Rails will continue to send a signal with what’s included in the core that this is a sideshow project. It satisfies some needs for some people and that’s great. But the goal of Rails is to create a world where they are neither needed or strongly desired. Obviously, we are not quite there yet.

One way of getting there is to do a better job of educating new comers in common patterns. Answer the question “if engines and components are not the way, then show me how!”. So this is a call to all those experts out there. Help us spread the good patterns. Make videos, write tutorials, help newbies on #rubyonrails, answer requests on the mailing list.

And if you have a great idea for an engine, or a high-level component in general, think about this: Is there a way I could abstract a smaller slice of functionality as an independent plugin and then release that alongside a pattern that described how to use it like the component would have done all in software? More often than not, I think you could find this to be true.

Note: James Adam, the creator of the engines approach, has a great post on the mailing list for how he uses engines internally at his company. That’s perfectly cool use. The trouble with high-level components are solely related to making them generic.

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