Rendering most recent articles rails 4 - ruby-on-rails

Question

Its currently listing my oldest articles at the top and I want to do the opposite. I think I need to order it as created_at somewhere but I have yet to make it work. I know this is easy but I'm still a newbie. Thanks
Currently I have
<div class="bit-75">
<h2 id="title"><%= link_to article.title, article_path(article) %></h2>
<br>
<ul id="article-links">
<div id="article-image"><%= image_tag article.image_url %></div>
<br>
<li id="article-text"><%= article.text %></li>
<br>
<%= article.created_at %>
<br>
<% if admin_signed_in? %>
<li><%= link_to 'Edit', edit_article_path(article) %></li>
<li><%= link_to 'Destroy', article_path(article),
method: :delete, data: { confirm: 'Are you sure?'} %></li>
<li><%= link_to 'New article', new_article_path %></li>
<% else %>
<li><%= link_to 'Make a Comment', article_path(article) %></li>
</ul>
<% end %>
article.rb
class Article < ActiveRecord::Base
has_many :comments, dependent: :destroy
validates :title, presence: true,
length: { minimum: 5 }
mount_uploader :image, ImageUploader
end
articles controller
def new
#article = Article.new
end
def index
#article = Article.all
end
def create
#article = Article.new(article_params)
if #article.save
redirect_to #article
else
render 'new'
end
end
def edit
#article = Article.find(params[:id])
end
def update
#article = Article.find(params[:id])
if #article.update(article_params)
redirect_to #article
else
render 'edit'
end
end
def show
#article = Article.find(params[:id])
end
def destroy
#article = Article.find(params[:id])
#article.destroy
redirect_to articles_path
end

Answer 1

In your Article model, article.rb, you can set a default_scope like this:
default_scope -> { order('created_at DESC') }
However, this method will sort the articles like this on all pages. If you only want to sort them like this on one action, say your def index, then something like this might work better.
#articles = Article.order('created_at DESC')
Like #ShamsulHaque said in his comment.
Here is a good read about default scopes.
Update
If you prefer to use scopes, like #rich says, then the syntax would look like this:
scope :recent, ->(order = 'desc') { order(created_at: order.to_sym) }
Which you would have the option, in your controller, to call either asc or desc like so:
#articles = Article.recent('asc')
#articles = Article.recent('desc') # although we defaulted to 'desc', so really only need Article.recent
To explain a bit, #rich included the to_sym to convert the string 'desc' or 'asc' to a symbol like :desc or :asc. If you did not do this, you would get an error like
Direction should be :asc or :desc
Hope this helps.

Answer 2

Scopes
Using default_scope is a little taboo (can cause problems) - you'll be much better using a standard scope with a condition:
#app/models/article.rb
Class Article < ActiveRecord::Base
scope :recent, (order = "desc") -> { where created_at: order.to_sym}
end
This will allow you to call:
#article = Article.recent("asc")
A nice extension to #justin's answer ;)