Just wanted to make a quick post that if you’re interested in Ruby on Rails Development, please contact me over at Velocity Labs instead of here. Thanks!

This past Tuesday evening I presented to the RubyAZ user group. The talk covered useful libraries and gems that I saw at Rails Conf 2012 that I thought others might find helpful in their day to day work. I’ve made the presentation slides available as a pdf. Enjoy!

I find it’s pretty annoying when you have to go log file spelunking only to find all the timestamps are in UTC.  But we can set the timezone of the server so when Rails, cron, scripts, etc run, they output more readable dates.

You can check your current timezone by just running

Or checking the timezone file at

So to change it just run

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.

UPDATE July 2016
In the comments Dan mentions that in 16.04 you use something like:

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Having problems getting ssh to use your public key?

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):

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

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.

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

Got burned by two things today in one of my apps by upgrading to Rails 3.1. The first thing was a few nested forms stopped working when editing an existing record that had child records. None of the children were getting rendered. For briefity, the form basically was like:

<%= 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

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

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

<%= 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

<% 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

ActionView::Template::Error (undefined local variable or method `view_context' for #<#:0x1057b9f70>):

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

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

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

In one of my current project, whenever I ran a rake task that did a net/http request it was causing segmentation faults.

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

And reinstall

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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I just ran into a rather hard to track down issue with Authlogic and Rails 3. After upgrading an old app to Rails 3, in production, the sessions wouldn’t persist, but everything worked fine in development mode. After much searching it turns out that there’s an issue with using Rails 3, Authlogic, and HTTP auth together. I had put up HTTP basic auth in Nginx to prevent the site from getting seen by random people or web crawlers. When the app was a Rails 2 app, there was no issue, in fact the Rails app shouldn’t even have known about the HTTP auth since I was doing it in Nginx, not Rails. Not sure why this is a problem with this Rails/Authlogic/HTTP combination, but anyways, the fix was to add this one-liner to your UserSession model

    1 class UserSession < Authlogic::Session::Base
    2   allow_http_basic_auth false
    3 end

In my Rails erb views I make good use of the dom_id view helper method. It basically introspects the object you pass to it and creates a unique id to use in your markup, based on the object type and database id. So for example if I had a Post with id 1, I could do:

    1 
    2 <li id="<%= dom_id(@post) %>">
    3 

And it would be rendered as

    1 
    2 <li id="post_1">
    3 

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:

/_(?!.*_)/

We can confirm in irb

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.

I’ve heard people describe frustrations they had in getting Rails 3 setup on Ubuntu 10.04 with Ruby 1.9.2. I’m going to outline the steps I’ve taken to do this. Let’s get started installing RVM.

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.

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

Cool, nada. Let’s grab the basic dependencies

Now we’ll install RVM as per their instructions

http://rvm.beginrescueend.com/rvm/install/

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

[ -z "$PS1" ] && return

with

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

Now add this to the last line of the file

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.

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

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.

Now we can look at all the RVM known Ruby packages

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.

Good to go.

On a project I’m currently working on, we use ActiveRecord callbacks heavily. From simplying creating other associated objects, to recording the historic activity about the object in question, and more.

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:

    1 class Post < ActiveRecord::Base
    2   belongs_to :user
    3   belongs_to :group
    4   has_one    :alert, :as => 'alertable'
    5
    6   after_update :note_activity
    7
    8   private
    9   def note_activity
   10     group.admins.each do |admin|
   11       # What user is doing this update?
   12       admin.notifications.create(:user => "Someone",
   13                                  :action => 'did something')
   14     end
   15   end
   16 end

    1 class Admin::PostsController < ApplicationController
    2
    3   def update
    4     @post = Post.find(params[:id])
    5
    6     if @post.update_attributes(params[:post])
    7       redirect_to admin_posts_path
    8     else
    9       render :action => 'edit'
   10     end
   11   end
   12 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:

    1 class ApplicationController < ActionController::Base
    2   before_filter :store_user
    3
    4   def store_user
    5     User.current = current_user
    6   end
    7 end

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

    1 class User < ActiveRecord::Base
    2
    3   def self.current=(user)
    4     Thread.current['user'] = user.try(:id)
    5   end
    6
    7   def self.current
    8     @@current ||= User.find_by_id(Thread.current['user'])
    9   end
   10 end

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

    1 def note_activity
    2   group.admins.each do |admin|
    3     admin.notifications.create(:user => User.current,
    4                                :action => 'did something')
    5   end
    6 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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