DRYing Up Preloads in Rails

As a Rails application grows, I’ve found that this pattern often emerges where we are repeating the same preloads across the application.

the problem

Whenever we add an association, or make a change. We have to update our preloads in multiple places. If we forget one, we’ve just introduced a potentially severe performance problem in our application.

(If you’re not familiar with includes/preloads/n+1's, read this. 😎)

We can DRY up this code by extracting it to a scope on the model.

We’ve been using this pattern in Product Hunt’s codebase for a few months now and I like it a lot.

Now in our code, we can use our new scope like this.

Another benefit of adding this scope to all of our models is that it starts to look strange to see a query without with_preloads. It acts as a nice reminder to double check everything is being correctly loaded.


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