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Include/Extend in Ruby Modules

April 23, 2011

I have always confused my self when to use include or extend when mixin methos of a class.

include() mixes methods into the instances of the base object.

extend() mixes methods into the base object itself.

For example,

module Color
  def green
    "I'm green"

By including Greeter into SomeClass, we make it so that we can now call hello() on instances of SomeClass.

class SomeClass
  include Color
end #=> "I'm green"

Extending AnotherClass with Greeter would allow us to call the hello method directly at the class level, as in the example below.

class AnotherClass
  extend Color
end #=> "I'm green"

Ruby Version Manager

October 23, 2009

I’ve been meaning to start using ruby1.9 but always stuck at maintaining codes in production that depends on Ruby1.8.6. Fortunately, there’s this thing called Ruby Version Manager where you easily change between different rails version. I have nothing but praise for the guys who made life easier for us programmers to do our job better & faster with RVM.

The only thing is you have to install your gems for each ruby version. It does make sense because there are quite a few gems that depends on different built. Installing gems are not that hard imho. So no issue there.

Now I can change between different ruby version as easy as this:

$ rvm 1.9.1 # For ruby 1.9.1

$ rvm 1.8.7

What’s excellent about this is the ruby version is sandbox in just that one terminal you’re using. It doesn’t interferes with your already *original ruby installation. * rvm calls is your ruby system. To revert back to your original ruby installation just do

$ rvm system

Or if you want to set a default ruby throughout your system. You can simply do so like this:

$ rvm 1.9.1 –default

If you haven’t tried it before, go try it. Don’t worry, it won’t mess up anything on your current ruby system

Ruby Version Manager –

Authlogic is Awesome

October 22, 2009

Have been tinkering around with authlogic. The most I love about is its out-of-the-box functionality. I used to wrestle with restful_authentication to get certain things that I need. Not in anyway that I’m bashing it but seeing how easy authlogic I couldn’t believe why I didn’t use it sooner.

I like it so much that I even made a rails template base on authlogic. This rails template has the usual basic signup/login/logout and I threw in some cucumber steps & stories in it. Here it is in flesh & bytes

Div’s does not wrap tr’s

September 16, 2009
tags: , ,

I tried to update a HTML div elevement wrapping around a table row inside a table.

<div id="placeholder">

I wasted 1 hour to find out why my ajax calls aren’t updating the right table row.

Apparently it’s not valid HTML. The div will always be on top and then the table tag.

A workaround that I found to put a placeholder id inside a table is by using <tbody>. So simply substitute the div with a tbody tag and you’re done.

My little contribution to a rails plugin (sort of)

June 14, 2009

Getting your bug fix/code pulled into the main repo really gets you excited & satisfied.

I never thought it could give me this much sense of enjoyment. Check it out.

Includes & Eager Loading

June 8, 2009

I’m figuring out something in my rails app.  I’m figuring out which one’s the worst:

Eager loading 100 rows of data you don’t actually need at the moment


10 queries giving 10 result set at once?

Here’s the code to explain it.

@event = Event.find(params[:event_id])

@event_attendees = @event.attendees.paginate(:page => params[:page], :per_page => 10)

In the view, for each attendees, it’s calling a purchase record. Since I’m using will_paginate and setting 10 records per page, for every 10 record of attendees, there’s 10 queries for a purchase record. Here’s the following SQL that will be generated:

SELECT * FROM `attendees` WHERE (`attendees`.event_id = 4)

SELECT * FROM `purchases` WHERE (purchasable_type = 'Attendee' and purchasable_id = 1) LIMIT 1
SELECT * FROM `purchases` WHERE (purchasable_type = 'Attendee' and purchasable_id = 2) LIMIT 1
SELECT * FROM `purchases` WHERE (purchasable_type = 'Attendee' and purchasable_id = 3) LIMIT 1
SELECT * FROM `purchases` WHERE (purchasable_type = 'Attendee' and purchasable_id = 4) LIMIT 1
SELECT * FROM `purchases` WHERE (purchasable_type = 'Attendee' and purchasable_id = 5) LIMIT 1
SELECT * FROM `purchases` WHERE (purchasable_type = 'Attendee' and purchasable_id = 6) LIMIT 1
SELECT * FROM `purchases` WHERE (purchasable_type = 'Attendee' and purchasable_id = 7) LIMIT 1
SELECT * FROM `purchases` WHERE (purchasable_type = 'Attendee' and purchasable_id = 8) LIMIT 1
SELECT * FROM `purchases` WHERE (purchasable_type = 'Attendee' and purchasable_id = 9) LIMIT 1
SELECT * FROM `purchases` WHERE (purchasable_type = 'Attendee' and purchasable_id = 10) LIMIT 1

Clearly you can that see the above code creates a n + 1 problem.

So I tried to modified it using eager loading like the following:

@event_attendees = @event.attendees.paginate(:include => :purchase, :page => params[:page], :per_page => 10)

Here’s the following SQL query generated:

SELECT * FROM `attendees` WHERE (`attendees`.event_id = 4)
SELECT `purchases`.* FROM `purchases` WHERE (`purchases`.`purchasable_id` IN (1,2,3,4..100) and `purchases`.`purchasable_type` = 'Attendee')
 # query is shorten for brevity

You can see that it’s using 1 query that fetches 100 rows of data. At first I thought that it will limit the eager loading with my will_paginate per page settings. But clearly for every page that I’m viewing, it’s calling that query hence returning 100 rows of data for each page I’m viewing.

At the moment I’m using the query without eager loading. Simply because I’m concern the app is fetching 100 rows that I don’t need at once. I have no idea how to limit an eager loading association base on will _paginate per_page. Or probably I could eager load once and keep in cache. Or does rails does that automatically?

Will investigate though. Oh well, back to work!

Routes Gotcha

December 18, 2008

Something peculiar happened when I was doing something trivial.

If you accidently named your restful route the following

resource :roles instead of resources :roles

When you point your app to /roles it won’t go to your index controller action but it will instead call your show action.