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New year resolutions

Pedro Teixeira — Wed, 30 Dec 2009 16:35:03 +0000

Happy new year to everyone!

I haven't posted for a while - had a busy end-of-year...

Things I want to look into early 2010:

Haml
Rails 3
Node.js
Erlang
Hadoop
Scala
EJB 3
Ruby alteranative VMs (JRuby, MacRuby, LevMag)
...and more cool blog posts!

sweepy – Distributed and scalable file caching expiration in Rails

Pedro Teixeira — Tue, 27 Oct 2009 23:13:00 +0000

Followin up on my post about Rails cache on a distributed environment, I recently published a Rails plugin called sweepy.

Sweepy allows you to expire file-based cache (page cache and fragment cache) on Rails on multiple boxes.

If you don’t want or don’t need to setup memcached, and just want to simply use Rails page and / or fragment caching, sweepy automatically handles page expiration.

You can use the Rails expire_page and expire_cache API, no need to change existing code.

…with the bonus of sweepy supporting a regexp as a expire_page argument.

Really, what is sweepy?

sweepy is two things:

A daemon running on each box
A Rails plugin to expire cache

sweepy is scalable

sweepy uses UDP broadcasts for cache cleaning. This way you can add as many machines as you want, and cache expiration times will remain the same.

Check out sweepy at github

How to alias_method_chain a class method on Rails

Pedro Teixeira — Fri, 16 Oct 2009 11:53:04 +0000

Sometimes, when building a plugin, you have to extend Rails behaviour using alias_method_chain.

So you do, on the included module:

...
    def self.included(base)
      base.send :include  InstanceMethods
      base.class_eval do
        alias_method_chain :method_i_want_to_extend, :my_feature
      end
    end

    module InstanceMethods
     def method_i_want_to_extend_with_my_feature(args)
       (do something or not...)
       method_i_want_to_extend_without_my_feature(args)
       (do something or not...)
     end
    end
...

What if the method you are extending is a class method?

Simple, just use the singleton class:

...
    def self.included(base)
      base.extend ClassMethods
      base.class_eval do
        class << self
          alias_method_chain :method_i_want_to_extend, :my_feature
        end
      end
    end

    module ClassMethods
     def method_i_want_to_extend_with_my_feature(args)
       (do something or not...)
       method_i_want_to_extend_without_my_feature(args)
       (do something or not...)
     end
    end
...

Tutorial – advanced styled_objects on Rails

Pedro Teixeira — Tue, 13 Oct 2009 11:19:04 +0000

Following the building and styling a Rails app with styled_objects tutorial, we will learn how to use some advanced features of styled_objects and also some best practices to keep your CSS code maintainable while using styled_objects.

Use CSS variables

On styled_objects you can define global variables to be used throughout your CSS.

Declare variables on one place: app/views/globals.css

Example of a piece of global.css that defines three variables:

@brand_color: #4D926F;
@base_color: #111;
@border-thickness: 1px;

Now, on any template or partial CSS file you can use these variables like this:

color: @brand_color;
border: @border-thickness solid @base_color;

styled_objects uses LESS on the background, so you can use LESS syntax, which is very similar to CSS. Be careful to only define global variables on a global file like application.css, so you can be sure the variable is present on all the included CSSs.

Code generic classes

OO-CSS says we should separate container styling from content styling. How can we do it using styled_objects?

Let's say you have a container for a box block that can be used throughout many partials. How to reuse this container?

What you need is a layout partial.

Create a app/views/containers/_box.html.erb with the container markup:

<%= yield %>

And create the respective CSS under app/views/containers/_box.css:

border: 2px solid #333;

That's it! No need for additional markup, (although you may need to if you have to decorate the box partial with images, for instance).

Now you only have to call your partials with a box layout like this:

<%= include :partial => 'article_summary', :layout => 'containers/box' %>
<%= include :partial => 'top_headlines', :layout => 'containers/box' %>

Debug your stylesheets

Introducing variables can lead to syntax errors that, because the final stylesheet is generated on the server, cannot be debug on a browser.

How to debug the result?

In development mode, when a change you made broke your stylesheet generation, you can:

Open the generated page source on your browser and look for something like