OLM On Rails

Posts Tagged ‘Rails

How to Install Seed_fu

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Today, we got a pretty awesome cursory code review from Mike Gunderloy.

One thing he suggested, was that we switch from running a sloppy Ruby script to seed our database with initial data, to something like seed_fu.

So, how do we install Seed_fu?  It took me a while to figure it out, actually, since I’d never installed a Rails plugin from GitHub before.

Anyhow, here’s how you do it:

From your application root:

script/plugin install git://github.com/mbleigh/seed-fu.git



Written by Mike Conley

June 11, 2009 at 5:07 pm

Posted in OLM on Rails

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Prototype/Ajax.Request -> Rails – The Plot Thickens Part 2

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Still no solution in sight.  I’ve tried creating a brand new Rails project, and the behaviour persists there as well.  I’m convinced it’s a problem with Rails though, and not a problem in my machine.

Let’s go over the facts again:

  • I have Rails 2.1.0 installed on an Ubuntu 8.04 Hardy Heron Tablet PC
  • I’m using a Postgres database on the OLM project
  • Using Prototype JS library V
  • We’re using Mongrel, not WeBRICK
  • Using Ajax.Request with the ‘POST’ method does not pass any parameters to the params hash in the target controller
  • It works with GET though!
  • When using POST, I can see the parameters if I inspect the request object – they’re in @parameters, which I cannot seem to access
  • POSTing seems to work on other computers, using the same OLM code checked out from the repository
  • I’ve tried a complete reinstall of Rails, with the same result

Maybe my uninstall assumption is wrong:  what’s the best way to completely purge Rails from my machine?  I essentially followed these steps before:

Thoughts from anybody?



Written by Mike Conley

November 21, 2008 at 3:04 am

Problems getting Prototype/Ajax.Request to talk to Rails

with 2 comments

I’m totally losing my mind over this problem, because it seems so simple, and yet I can’t seem to figure it out.

Here’s the situation:

I’ve begun linking up my Rubric Manager UI prototype to the Rails backend.  On this UI is a big “Save Changes” button, that implements all of the changes to the Rubric in one shot.  That button is linked to a Javascript function called save_changes.

Here is save_changes:

function save_changes() {
/* ....some code...*/
  new Ajax.Request('/checkmark/rubrics/modify',
      parameters: {authenticity_token: '<%=form_authenticity_token%>', key: 'value'},
      onSuccess: function(transport){
  onFailure: function(){ console.error('Something went wrong...') }
/*...some more code...*/

So this seems alright to me.  I have to include the “authenticity_token” in my parameters because Rails seems to be using some type of internal request forgery protection.

When I click on “Save Changes”, however, Firebug tells me that the page I POSTED to threw an “InvalidAuthenticityToken” exception.  So that’s frustrating – I’m clearly passing the token in my parameters.  I created a tiny test form and POSTed to the same ‘modify’ method with the authenticity token as a hidden value, and it worked just fine.

So what gives?

Geofrey helped me get by the InvalidAuthenticityToken problem by inserting the authenticity_token variable into the URL string of the Ajax.Request target:

function save_changes() {
/* ....some code...*/
  new Ajax.Request('/checkmark/rubrics/modify?authenticity_token=43e5f5e3fbf3248b2a403f828010f8544ad36dbf',
      parameters: {key: 'value'},
      onSuccess: function(transport){
  onFailure: function(){ console.error('Something went wrong...') }
/*...some more code...*/

But NOW, the parameter “key => value” isn’t being passed to the rails param map in the RubricsController.  I know this, because I inspect the param map in the Controller with the following code:

def modify
    render :text => params.inspect  

And here’s what is returned from the AJAX call:

{"authenticity_token"=>"43e5f5e3fbf3248b2a403f828010f8544ad36dbf", "action"=>"modify", "controller"=>"rubrics"}

So what’s going on?  Anyone.


Written by Mike Conley

November 14, 2008 at 12:41 am

Posted in Uncategorized

Tagged with , , , , ,

Developing a Rubric for OLM on Rails

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Hey all – I’m Mike, and I’ve just started working on the OLM on Rails project.  My first task is to develop the Rubric models, controllers, and user experience, and I’m going to share some musings on it.

Ok, so first off, here’s the idea:  A professor creates an Assignment, and has to have a marking scheme to go along with it.  The Rubric that she develops will be used by the TA’s to mark the assignments.  Sounds pretty simple.

I’m still getting my thinking wrapped together here, so I’m just going to muse for a bit.  Here are some thoughts, rules, and caveats:

  • Creation of a Rubric is a separate event from creating an Assignment.  So if an Assignment exists, it does not imply that an associated Rubric exists yet
  • A Rubric consists of an arbitrary number of criteria to grade the student
  • Each criterion has a weight assigned to it (ie: 0.25, 0.5, etc)
  • Each criterion has a number of levels that can be achieved by a student.  By default, these levels are 0, 1, 2, 3, and 4 – with 0 being the worst performance, and 4 being the best.  We’re considering having the ability to add additional levels, to improve flexibility
  • An assignment cannot be marked until a Rubric has been created
  • A Rubric is not valid unless all of the weights of its criteria sum to 1.0 (100%)
  • The total number of marks achievable on an Assignment equals the sum of each criterion weight, multiplied by the maximum level of that criterion.  This does not include possible bonus marks, which are not handled by the Rubric
  • Assigning weights to criteria is going to be a little tricky, interface-wise.  While it’s tempting to just use a simple text-box, and trust the user to input the weights manually, it’d be nice for something a little more elegant and user friendly.
  • Some professors may want a simpler way of inputting this information quickly, for instance, by uploading a file describing what they want.  Andrew has suggested that users upload a YAML file… something worth thinking about.

That’s all I’ve really got rolling in my head about it right now.

So, what have I done?  I’ve created two new models:  RubricCriteria and RubricLevel.  A RubricCriteria is assigned to a single Assignment.  A RubricLevel is assigned to a single RubricCriteria.  Piece of cake.

I’ve also created some basic unit tests for these models.  I think I’m going to start thinking about user interfaces now, because I think it will give me some hints on what I’ll want the Controller to do.  I might upload some of my sketches later.



Written by Mike Conley

October 8, 2008 at 12:43 pm

Posted in OLM on Rails

Tagged with , , , , , ,

Switching Rails to PostgreSQL

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Since most of the web applications we develop here uses PostgreSQL, we’ve decided to port our environment to use postgres instead. Here I outline how I managed to get rails and PostgreSQL 8.3 up and running on Ubuntu 8.04.

1. Install PostgreSQL

If you haven’t already, try typing:

sudo apt-get install postgresql postgresql-client postgresql-contrib libpq-dev

Make sure that the installation completed successfully by typing psql --version. Current version is 8.3.3. libpq-dev is important since the postgres gem needs it, so make sure that we have that installed even if you have postgresql installed already.

2. Install PostgreSQL adapter for ruby

Update your rubygem first by typing sudo gem update --include-dependencies. You then need to install ruby-pg, which superseded the now-obsolete ruby-postgres gem (which can’t even compile postgres 8.3 due to a compilation bug). To install postgres gem, type:

sudo gem install postgres

3. Create a PostgreSQL user

By default, the user in the rails DB config file is the project name. Thus we can create this user by going into the postgres console

sudo su postgres -c psql

Once in the psql console, type (including the quotes)

create user "<user_name>" with [superuser] password '<password>';

Include the superuser option if needed, usually easier for development when working on your own computer. Verify that the CREATE ROLE message was displayed then exit the console.

4. Change PostgreSQL Authentication

When executing some of the database commands, you might encounter a FATAL: ident authentication failed error. To avoid this, you need to edit your pg_hba.conf (found in /etc/postgresql/8.3/main in Ubuntu 8.04) and change the authentication scheme. Open the file with root privilege and change

# "local" is for Unix domain socket connections only
local all all ident sameuser


# "local" is for Unix domain socket connections only
local all all md5

Then restart your postgres server by typing sudo /etc/init.d/postgresql-8.3 restart

5. Create the databases

to create the database we can use the createdb shell command, by typing on prompt:

createdb <project_name>_development -U <user_name> -W

or, if user does not have superuser account, from the psql console (by sudo’ing as postgres from before) typing:

create database <project_name>_development owner <user_name>;

and give privilege to the user by typing:

grant all privileges on database <database_name> to <user_name>;

Do the same thing for creating <project_name>_test for the test database.

5.5 Install phppgadmin (optional)

To make your life easier, there’s a php console for developing with postgres called phppgadmin, derived from its MySQL counterpart, phpmyadmin. phpmyadmin is still a lot better interface, but phppgadmin is better than nothing at all. Assuming you have PHP and apache2 installed, install phppgadmin by typing:

sudo apt-get install phppgadmin

and create a symlink for apache:

sudo ln -s /etc/phppgadmin/apache.conf /etc/apache2/conf.d/phppgadmin.conf

Reload apache by typing sudo /etc/init.d/apache2 reload and go to http://localhost/phppgadmin/ to play around with your new tool.

6. Generate a database config file for PostgreSQL

If you’re starting from scratch, the easiest way is to create your application using

rails <project_name> -d postgresql

However, if we’re migrating to postgres from a current rails application, then the easiest way is to just create another rails application of the same name but on a different directory. Go to a directory where your current rails application is not located and create a rails application of the same name using above command. Once that’s created, just copy the database config file to your old rails application by copying:

mv <original_project_path>/config/database.yml <original_project_path>/config/database.yml.old

cp <project_name>/config/database.yml <original_project_path>/config

Once copied, open database.yml on a text editor and fill in the database details we just created.


One of the problems I encountered was figuring out which postgresql adapter to use. ruby-postgres wasn’t working with postgres 8.3 so I regressed back to 8.2, only to find out postgres adapter exists. Not much documentation exists since it’s fairly new and a lot of people I guess is still in psql-8.2. The other one is the dreaded FATAL: ident authentication failed error you get when starting to use psql on Ubuntu. Again, thanks to Jeff and the Dr. Project documentation, we finally got it working.

And finally, psql-8.3 seems to break the implicit cast being done from the previous 8.2 before.  So now, when I try to find matches where numbers are stored as string, I get the following error:

ERROR:  operator does not exist: character varying = integer

The column being declared as string does not match the passed integer argument, which should be converted to String in the first place.  Thus I had to explicitly cast it to a String before using.

For more information regarding PostgreSQL and Ruby on Rails, see the official wiki.

Written by Geofrey

August 12, 2008 at 10:22 am

Migrate Your Tests

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Rails has a nice way of maintaining versions of your database schema through ActiveRecord:Migration.  This lets you modify your existing schema without the hassle of manually copying the same schema to all the different deployed instances that you have, and does this automatically for you.

When I usually change the schema, I usually drop all the tables and recreate them using:

rake db:migrate VERSION=0
rake db:migrate

and then repopulate my development DB environment using a script I use.  However it turns out that this doesn’t migrate your test environment automatically with it. I tried creating a simple test of making sure that my ActiveRecord validation works.  However, I ended up getting this error:

NoMethodError: undefined method `group_limit=' for #<Assignment:0xb7242018>
/var/lib/gems/1.8/gems/activerecord-2.1.0/lib/active_record/attribute_methods.rb:251:in `method_missing'
test/unit/assignment_test.rb:11:in `test_numericality_group_limit'
/var/lib/gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:33:in `__send__'
/var/lib/gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:33:in `run'

After hours of finding the bug, I found out that you have to migrate your test DB environment as well, by executing the following:

rake db:schema:dump
rake db:test:prepare

This will copy the schema that you have right now in your development environment, and copy it to your test environment.

Written by Geofrey

August 6, 2008 at 10:49 am

Pay Attention to Little Things

with one comment

On testing:

If you ever tried running your tests and find yourself getting the error:

your_controller_test.rb:3:in `require': no such file to load -- test_helper (LoadError)
from your_controller_test.rb:3

it’s probably because the generated require call, require test_helper is not being properly recognized.  Instead of the default require 'test_helper', replace it with:

require File.dirname(__FILE__) + '/../test_helper'

If you’re doing functional testing, make sure that the controller being tested is also required (e.g. add the line require 'your_controller' on top).  Be sure that you also have installed the package libtest-unit-ruby (if using Linux), before testing.

Also, thanks to Jeff Balogh, make sure that you append test_ on all your test cases to make sure that they actually run (I know it’s obvious, but it’s nice to be reminded once in a while).

On database constraints:

If you want to enforce foreign key constraints, remember to create the required indexes first.  ActiveRecord Migration supports this using add_index.  This only applies if the column being referred to is not a primary key, if it is then there’s no need to create the index. Once this is set, you can now enforce foreign keys using ActiveRecord Migrations by implementing this.

On implementing sessions:

By default, the rails session handler stores session information on a file in the server.  This can cause scalability issues in the long run if file space runs out or when using multiple servers.  Thus, it’s recommended to use :active_record_store instead. To do this make sure that you do the following:

  • execute rake db:sessions:create to add a create table migration for sessions
  • execute rake db:migrate to apply the new schema
  • change session store to active session store by adding this line to config/environment.rb:

config.action_controller.session_store = :active_record_store

  • Make sure that you comment out or add this line to your ApplicationController:

protect_from_forgery :secret => <32_hex_digit_secret_key>

Here are also some helpful links regarding sessions and implementing it:

Written by Geofrey

July 29, 2008 at 4:01 pm