Forward ActiveRecord::Relation#count to Enumerable#count if block given

[sferik]

I came across this line of code today:

class Order
  has_many :deliveries

  def num_deliveries_in_progress
    deliveries.select { |delivery| delivery.in_progress? }.size
  end

end

I had the idea to refactor this to use Enumerable#count, which takes a block, instead of Enumerable#select followed by Array#size.

 class Order
   has_many :deliveries

   def num_deliveries_in_progress
+    deliveries.count { |delivery| delivery.in_progress? }
-    deliveries.select { |delivery| delivery.in_progress? }.size
   end

 end

What happened instead was this method always returned the count of all the deliveries for that order (even counting ones that are not in progress) because ActiveRecord::Relation#count silently discards the block argument.

This is a similar situation to ActiveRecord::Relation#find, which collides with Enumerable#find, however, in that case, super is called.

[rails-bot]

r? @kaspth

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[kaspth]

Documentation is now outdated, we don't always count in SQL.

[kaspth]

LGTM, but requires a doc update 😁 — ping me when you got 'em 😉

[sferik]

@kaspth Thank you for reviewing. I have added documentation for passing a block to ActiveRecord::Relation#count. Please let me know if there is anything else that needs to be done.

[kaspth]

Think this would follow more logically by being moved just above.

[kaspth]

Had some more comments about the docs. Remember to squash your commits 😁

[sgrif]

Just as a reminder, we are way past the feature freeze for Rails 5. This shouldn't be merged until after 5 is branched from master.

[sferik]

@kaspth I’ve fixed up the documentation as you’ve suggested and amended those changes to the previous commit. If you’d prefer, I can squash everything into a single commit.

[sferik]

@sgrif I didn’t realize the Rails 5 feature freeze was in effect but that makes sense, considering you’ve already started shipping betas. I’m a little disappointed this feature won’t make it into Rails 5.0 but I’m excited to have it be one of the first features merged into Rails 5.1! 😄

[kaspth]

@sferik yeah, all the way down to one commit please.

I’m excited to have it be one of the first features merged into Rails 5.1!

You can bet your editor, it is! 😉

[sferik]

@kaspth Done.

[kaspth]

There we go, merged after master is 5.1 😁