Ruby on Rails: grouping blog posts by month

Question

Hy guys. I've created a simple blog app with the usual CRUD actions. I've also added a new action in the PostController called "archive" and an associated view. In this view I want to bring back all blog posts and group them by month, displaying them in this kind of format:

March
<ul>
    <li>Hello World</li>
    <li>Blah blah</li>
    <li>Nothing to see here</li>
    <li>Test post...</li>
</ul>

Febuary
<ul>
    <li>My hangover sucks</li>
    ... etc ...

I can't for the life of me figure out the best way to do this. Assuming the Post model has the usual title, content, created_at etc fields, can someone help me out with the logic/code? I'm very new to RoR so please bear with me :)

Answer 1

group_by is a great method:

controller:

def archive
  #this will return a hash in which the month names are the keys, 
  #and the values are arrays of the posts belonging to such months
  #something like: 
  #{ "February" => [#<Post 0xb5c836a0>,#<Post 0xb5443a0>],
  # 'March' => [#<Post 0x43443a0>] }
  @posts_by_month = Posts.find(:all).group_by { |post| post.created_at.strftime("%B") }
end

view template:

<% @posts_by_month.each do |monthname, posts| %>
<%= monthname %>
<ul>
   <% posts.each do |post| %>
     <li><%= post.title %></li>
   <% end %>
</ul>
<% end %>

Answer 2

@Maximiliano Guzman

Good answer! Thanks for adding value to the Rails community. I'm including my original source on How to Create a Blog Archive with Rails, just in case I butcher the author's reasoning. Based on the blog post, for new developers to Rails, I'd add a couple suggestions.

First, use Active Records Posts.all method to return the Post result set for increased speed and interoperability. The Posts.find(:all) method is known to have unforeseen issues.

Finally, along the same vein, use beginning_of_month method from the ActiveRecord core extensions. I find beginning_of_month much more readable than strftime("%B"). Of course, the choice is yours.

Below is an example of these suggestions. Please see the original blog post for further detail:

controllers/archives_controller.rb

def index
    @posts = Post.all(:select => "title, id, posted_at", :order => "posted_at DESC")
    @post_months = @posts.group_by { |t| t.posted_at.beginning_of_month }
end

views/archives/indext.html.erb

<div class="archives">
    <h2>Blog Archive</h2>

    <% @post_months.sort.reverse.each do |month, posts| %>
    <h3><%=h month.strftime("%B %Y") %></h3>
    <ul>
        <% for post in posts %>
        <li><%=h link_to post.title, post_path(post) %></li>
        <% end %>
    </ul>
    <% end %>
</div>

Good luck and welcome to Rails!