You can check your current timezone by just running

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date
Thu Mar 21 18:02:49 MST 2012

Or checking the timezone file at

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more /etc/timezone
US/Arizona

So to change it just run

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sudo dpkg-reconfigure tzdata

And follow on screen instructions.  Easy.

Also be sure to restart cron as it won’t pick up the timezone change and will still be running on UTC.

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/etc/init.d/cron stop
/etc/init.d/cron start

Log on to your server as root using a password. Remember not to log out as root until you have ssh working with your public key or you may inadvertently lock yourself off the box.. which sucks ;) Double check your sshd_config, I use the following options (note you will have to restart ssh for these changes to take effect):

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Port 30000    <--- change to a port of your choosing
Protocol 2
PermitRootLogin no
PasswordAuthentication no
UseDNS no
AllowUsers deploy   <--- change to whatever users you want
ClientAliveInterval 30
ClientAliveCountMax 4

Make sure your public key is in the .ssh/authorized_keys file for the user you plan on logging onto the server as. You can use this super helpful authme bash function.

So let’s say you’ve done all this and YOU STILL CAN’T get it to work. It’s probably because you have incorrect permissions set on the .ssh directory and/or the authorized_keys file. You can check this by looking at the ssh auth log. Depending on your server OS it’s usually either /var/log/auth.log or /var/log/secure . Tail this file and see if you’re getting this message

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Authentication refused: bad ownership or modes for directory /home/deploy/.ssh

Obviously your directory will be different depending on the name of the user you’re trying to ssh on as. But this message is the give away that your permissions are wrong. Change them with the following, assuming your username is “deploy”, otherwise just substitute that part.

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chmod go-w /home/deploy/
chmod 700  /home/deploy/.ssh
chmod 600  /home/deploy/.ssh/authorized_keys

Try ssh’ing on again in another terminal window and you should be good. Now it would be safe to log off as root.

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<%= form_for @meal do |meal_form| %>
  <table>
    <tbody>
      <% meal_form.fields_for :meal_items do |item_form| %>
        <%= render :partial => 'meal_item_fields',
                   :locals => { :f => item_form } %>
      <% end %>
    </tbody>
  </table>
<% end %>

Can you spot the error? Once I spotted it I felt rather dumb myself. It’s the following erb tag

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<% meal_form.fields_for :meal_items do |item_form| %>

Ya even when they’re nested you HAVE to use the <%= form… doh!

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<%= meal_form.fields_for :meal_items do |item_form| %>

The second problem I ran into, and which I still don’t have an answer for, though if you do answer my StackOverflow question. Basically, in Rails 2.3 if you needed to get at an instance of the Template Builder you could use @template, but then they changed it in Rails 3 to a special method called “view_context”. Far enough, so I was using view_context in Rails 3.0.X to create nested forms (other than the one above) dynamically using jQuery ajax and js.erb partials. Using view_context allowed me to call fields_for off of it so that I would get nicely named form_fields when I didn’t have the parent FormBuilder handy. Like this

In some_view.js.erb

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<% fields =
    view_context.fields_for :meal_items, Meal.new.meal_items.new do |f|
      render :partial => 'meal_item_fields', :locals => {:f => f}
    end %>

$("#meal-items").append("<%= escape_javascript(fields) %>");

But once I upgrade to 3.1, I started getting the following error

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ActionView::Template::Error (undefined local variable or method `view_context' for #):

Perhaps this was removed as the Core team figured, why do you need the view_context available when you’re in a view template already… but I don’t know. I was able to workaround it though by moving my code up into the controller. Which does seem to be a violation of the MVC separation, but I couldn’t find any other way to make it work like pre Rails upgrade. So instead of creating a local variable “fields”, this became an instance variable that was set in the controller action. And render needed to become render_to_string with an html_safe call tacked on the end.

In controller

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def some_ajax_action
  @fields =
    view_context.fields_for :meal_items, Meal.new.meal_items.new do |f|
      render_to_string(:partial => 'fields', :locals => {:f => f}).html_safe
    end
end

I don’t like this, but it’ll do for now I suppose. And now in some_view.js.erb

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$("#meal-items").append("<%= escape_javascript(@fields) %>");

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bundle exec rake test:task
/Users/cirish/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/net/http.rb:678: [BUG] Segmentation fault
ruby 1.9.2 (2011-06-30 patchlevel 290) [i686-darwin10.8.0]

And it seems whenever I get a segmentation fault the first place I need to look is at OpenSSL. I’ve had similar problems with seg faults and openssl in the past, namely this OpenSSL Bus Error that I was getting on Ruby 1.8.7.

If you read that post you’ll see this happened because I use MacPorts and have OpenSSL installed through it, in addition to a local OS X version. To get Ruby to be happy, you have to point your Ruby install to the correct version at installation time. So remove the bad install

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rvm remove ruby-1.9.2

And reinstall

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rvm install ruby-1.9.2 --with-openssl-dir=/opt/local --with-iconv-dir=$rvm_path/usr

Which I forgot to do with my Ruby 1.9.2 install after upgrading OS X versions. That last bit about iconv isn’t directly related, but I have inconv package installed to RVM, you can read about that here RVM Iconv.

Also, this Phusion blog post REE 1-8-7-2011-03-released mentions problems with OpenSSL and MacPorts. Moral of the story… use HomeBrew? Dunno, but I’ll probably start using it when I upgrade my laptop.

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<li id="<%= dom_id(@post) %>">

And it would be rendered as

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<li id="post_1">

This is fine until you use dom_id on an object with a compound name like EmailNotification. Now dom_id will create a unique id like

email_notification_1

Which is still good until I’m doing some front-end testing and I’m parsing these dom ids to find their related db records. Now I need to split “email_notification_1” in a way that easily separates the object class from the identifier. How would you do that?

Well, what we can do here is use an advanced Regular Expression feature called a negative look ahead. We want to say, “split the string on the last underscore”.

A negative look ahead uses the ?! syntax in parenthesis, everything that follows ?! in the parenthesis will be used in the negative look ahead matching. So in our case we want to say, there should be a underscore that can be followed by any character except another underscore. The pattern would like like this:

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/_(?!.*_)/

We can confirm in irb

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ree-1.8.7-head > x = "email_notification_1234"
 => "email_notification_1234"
ree-1.8.7-head > klass, id = x.split(/_(?!.*_)/)
 => ["email_notification", "1234"]

Likewise, If we wanted to split the dom_id on the first underscore we could just use a regular look ahead. It is similar but uses the ?= syntax.

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ree-1.8.7-head > x.split(/_(?=.*_)/)
 => ["email", "notification_1234"]

It should be noted that I created a fresh slice on my Rackspace Cloud account to create this tutorial. And I’m assuming you’ve already setup SSH.

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ssh root@173.XXX.XXX.XXX
<-- Output Snipped -->
root@173.XXX.XXX.XXX's password:
<-- Output Snipped -->

Alright, so lets confirm we don’t have ruby installed

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which ruby

Cool, nada. Let’s grab the basic dependencies

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sudo apt-get install curl git-core ruby
Reading package lists... Done
Building dependency tree
<-- Output Snipped -->

Now we’ll install RVM as per their instructions
http://rvm.beginrescueend.com/rvm/install/

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bash -s stable < <(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer )

<-- Output Snipped -->

RVM:   shell scripts which allow management of multiple ruby interpreters and environments.
RTFM:  http://rvm.beginrescueend.com/
HELP:  http://webchat.freenode.net/?channels=rvm (#rvm on irc.freenode.net)

* Installing rvm to /usr/local/rvm/
    Correct permissions for base binaries in /usr/local/bin...
    Copying manpages into place.

Notes for Linux ( DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=10.04
DISTRIB_CODENAME=lucid
DISTRIB_DESCRIPTION="Ubuntu 10.04 LTS" )

<-- Output Snipped -->

    *  For JRuby (if you wish to use it) you will need:
       $ aptitude install curl sun-java6-bin sun-java6-jre sun-java6-jdk
    *  For MRI & ree (if you wish to use it) you will need (depending on what you are installing):
       $ aptitude install build-essential bison openssl libreadline5 libreadline-dev curl git-core zlib1g zlib1g-dev libssl-dev vim libsqlite3-0 libsqlite3-dev sqlite3 libreadline-dev libxml2-dev git-core subversion autoconf
    *  For IronRuby (if you wish to use it) you will need:
       $ aptitude install curl mono-2.0-devel

<-- Output Snipped -->

WARNING:  you have a 'return' statement in your .bashrc, likely this will cause untold havoc.
   This means that if you see '[ -z "$PS1" ] && return' then you must change this line to:
   if [[ -n "$PS1" ]] ; then
     ... original content that was below the && return line ...
   fi # <= be sure to close the if.
   #EOF .bashrc
Even if you use zsh you should still adjust the .bashrc as above.
If you have any questions about this please visit #rvm on irc.freenode.net.

Installation of RVM to /usr/local/rvm/ is complete.

The last part in there about the .bashrc file is important! Using your editor of choice, open the .bashrc file that resides in your user directory.

You need to replace the line that says

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[ -z "$PS1" ] && return

with

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if [[ -n "$PS1" ]]; then

Now add this to the last line of the file

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if [[ -s $HOME/.rvm/scripts/rvm ]] ; then source $HOME/.rvm/scripts/rvm ; fi

fi

And yes there needs to be that last fi as it closes the one we added earlier. Save this file with our changes. Now we can check if RVM is setup correctly.

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rvm notes

If this doesn’t work you may have to source your .bashrc file to have it reloaded by the current terminal session

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source ~/.bashrc

After running rvm notes if it gives you installation notes about RVM then you’re good to continue, otherwise double check you edited your .bashrc file correctly.

In the notes output RVM tells you what packages you’re gonna need to install for various flavors of Ruby. Since we’re going with 1.9.2 we want the packages it lists under the MRI & ree section. Let’s install those now.

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sudo aptitude install build-essential bison openssl libreadline5 libreadline-dev curl git-core zlib1g zlib1g-dev libssl-dev vim libsqlite3-0 libsqlite3-dev sqlite3 libreadline-dev libxml2-dev git-core subversion autoconf

<-- A really long bit of Output Snipped -->

Now we can look at all the RVM known Ruby packages

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rvm list known
# MRI Rubies
(ruby-)1.8.6(-p399)
(ruby-)1.8.6-head
(ruby-)1.8.7(-p302)
(ruby-)1.8.7-head
(ruby-)1.9.1-p243
(ruby-)1.9.1-p376
(ruby-)1.9.1(-p429)
(ruby-)1.9.1-head
(ruby-)1.9.2-preview1
(ruby-)1.9.2-preview3
(ruby-)1.9.2-rc1
(ruby-)1.9.2-rc2
(ruby-)1.9.2(-p0)
(ruby-)1.9.2-head
ruby-head

# JRuby
jruby-1.2.0
jruby-1.3.1
jruby-1.4.0
jruby-1.5.1
jruby(-1.5.2)
jruby-head

<-- Output Snipped -->

Next we install the version we want and set it as the default. You’re gonna see RVM install ruby-1.8.7-p302 first, be patient as it will need to also install rubygems-1.3.7, before it finally gets to that 1.9.2.

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rvm install 1.9.2-head
<-- Output Snipped -->
info: Installing ruby-1.8.7-p302
<-- Output Snipped -->
info: Installing rubygems dedicated to ruby-1.8.7-p302...
<-- Output Snipped -->
info: Installing ruby-1.9.2-head
<-- Output Snipped -->
info: Updating rubygems for /usr/local/rvm/gems/ruby-1.9.2-head

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rvm --default 1.9.2-head
ruby -v
ruby 1.9.2p0 (2010-08-18 revision 29034) [x86_64-linux]

Good to go.

The drawback I find from the scope of AR callbacks though is that you only have direct access to data from the database. And since you can’t pass arguments to a AR callback, you can’t easily get the request params for example or know which controller action fired off the the AR chain that triggered the callback you’re in, or know who the current user logged in is.

But it turns out that there is a way, however it is neither straight forward or obvious. Say for example you have the following model and controller:

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class Post < ActiveRecord::Base
  belongs_to :user
  belongs_to :group
  has_one    :alert, :as => 'alertable'

  after_update :note_activity

  private
  def note_activity
    group.admins.each do |admin|
      # What user is doing this update?
      admin.notifications.create(:user => "Someone",
                                 :action => 'did something')
    end
  end
end

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class Admin::PostsController < ApplicationController

  def update
    @post = Post.find(params[:id])

    if @post.update_attributes(params[:post])
      redirect_to admin_posts_path
    else
      render :action => 'edit'
    end
  end
end

What we want to accomplish here is that all admins of a group get a notification when another admin user edits a post. The post in question here has no context in it’s callback of which admin was logged in at the time the update happened. So what we’re gonna do is put the admin user’s id onto the current thread of the request in a before filter. Then, we’ll pull that id off in the callback to look up the admin and create the notifications.

So we’ll add a simple before filter:

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class ApplicationController < ActionController::Base
  before_filter :store_user

  def store_user
    User.current = current_user
  end
end

And create a couple class methods on User to store the currently logged in admin for the duration of the request:

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class User < ActiveRecord::Base

  def self.current=(user)
    Thread.current['user'] = user.try(:id)
  end

  def self.current
    @@current ||= User.find_by_id(Thread.current['user'])
  end
end

Now we can alter our note_activity method in Post to get the admin who did the edit:

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def note_activity
  group.admins.each do |admin|
    admin.notifications.create(:user => User.current,
                               :action => 'did something')
  end
end

This works well in my project. I’d like to know if there is a less “hacky” way of doing this but I’m not currently aware of one.

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string = mode.to_s
string.gsub!(%r{(^.)|(_.)}) { |m| m[m.length-1,1].upcase }

Two things struck me about that second line. For one I’ve never used gsub and passed it a block, thats cool. And two, what is %r{} ? I’ve never seen that before. It turns out that in Ruby, the /…/ or %r… literals, and using the Regexp.new constructor are all the same thing. All ways of created a regular expression. I still think I prefer the look of the simple slashes /…/ though.