#Preface

Being a PHP developer for more than 5 years I recently started learning Ruby on Rails. While I'm used to "Convention over Configuration" principles in PHP frameworks I found not a few conventions in Ruby on Rails that amazed me in some way.

There is something that amazed me more than anything else and I couldn't help myself from writing about it when I discovered it in this book written by Michael Hartl.

#Render a partial for model objects

Assuming we have a simple Controller action:

def index
  @users = User.all
end

..and a simple partial template called _user.html.erb:

<p><%= user.name %></p>

..let's take a look at it's View (index.html.erb):

<% @users.each do |u| %>
  <%= render 'user', user: u %>
<% end %>

Here, a partial _user.html.erb that resides in the same directory as current template file is being rendered for every @users element. Pretty straight-forward. Similarly I would do it in any PHP framework.

However as it turns out View's code can be replaced with just one line:

<%= render @users %>

It looks simple and logical at first sight, however, if you think about it, there are so many things happening in this line.

Let's break it into pieces:

• Rails infers that @users is a list of User objects.
• Because @users is a list Rails iterates through every element.
• Because @users consists of User objects it assigns every object to partial's variable user and renders a partial called _user.html.erb

If @users would be a list of Post objects, Rails would set partial's variable called post and render a partial called _post.html.erb for every list element.

#Conclusion

I'm a big fan of convention over configuration paradigm and such examples excite me every time I discover them. I know it slows down the learning progress in the beginning but it saves time in the long run.