Grouping and sorting Active Records in Ruby

I have made a few changes to my blog recently, one of them being a list of posts on the right hand side. I had some difficulties with it as I am still new to Ruby and couldn’t find any examples. So here is mine, this is a nice simple way to group Posts by year and month.

<% Post.all
        .group_by{|ar| ar.created_at.strftime "%Y %b" }
           .each do |date_str, post_for_month| %>
  <%= date_str %>
 
    <% post_for_month.each do |post| %>
     <%= link_to(post.title, post_path(post)) %>
    <% end %>
 
<% end %>

The expected output will be

2011 January

post title one
post title two

2011 February

post title one

If you want to sort by date as well simply change the code above to this

<% Post
       .order("created_at DESC")
         .group_by{|ar| ar.created_at.strftime "%Y %b" }
            .each do |date_str, post_for_month| %>
  <%= date_str %>
 
    <% post_for_month.each do |post| %>
     <%= link_to(post.title, post_path(post)) %>
    <% end %>
 
<% end %>

More information can be found here and here

-Matt

June 3, 2011 ·