Ruby sorting issue

Question

I'm trying to sort the array @users by the number of posts they have. Here's what I have in my controller:

@users = User.includes([:posts]).where("user_type = ?", "A")        
@users.sort {|a,b| (a.posts.size <=> b.posts.size)}

Here's what I have in my view:

<% @users.each do |user| %>
  <%= user.name %>: <%= user.posts.size %>
  <br>
<% end %>

My list of users is pretty random and is not properly sorted. If I'm not mistaken, the <=> operator is what I want to use. I want to return 1 if a has more posts than b, -1 if b has more posts than a and 0 if a and b have the same number of posts.

iltempo · Accepted Answer · 2013-02-06 21:49:15Z

4

It's just the missing bang.

@users.sort! {|a,b| (a.posts.size <=> b.posts.size)}

answered Feb 6, 2013 at 21:49

iltempo

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Logan Serman · Accepted Answer · 2013-02-06 21:49:27Z

2

You are using sort instead of sort!. sort! will sort @users in place.

answered Feb 6, 2013 at 21:49

Logan Serman

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the Tin Man · Accepted Answer · 2013-02-06 22:38:13Z

0

Two things I see:

Instead of using sort, use sort_by when you have to dig into an object. It shouldn't be a big speed up for the short method chain you're using, but it can add up:

@users.sort_by! {|a| a.posts.size }

If you're retrieving your data from the database, instead of sorting in Ruby, use order or order_by, depending on which is supported, to have the DBM sort the data in the order you want. DBMs are optimized for sorting and can do it extremely fast.

edited Feb 6, 2013 at 22:38

answered Feb 6, 2013 at 22:32

the Tin Man

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1 Comment

Ringo Blancke Over a year ago

I would love to use order or order_by ... but I need to order by the size of a separate query.

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