hectorsq

factory_girl Validation failed

2011-09-24T00:00:00+00:00

Using factory_girl to create several instances of a class that belongs to another class causes a Validation failed error.

This happens because each instance tries to automatically create the object to which it belongs. However since the first instance creates it, the following instances crash because the object already exists.

I have been struggling to solve this problem and it seems finally I arrived to a satisfactory solution.

The problem arises when there is a one to many relationship between to classes and I try to create several instances of a class.

In my case I have a subdomain which has many users:

class Subdomain < ActiveRecord::Base
  validates_uniqueness_of :name, :case_sensitive => false
  has_many :users
end
class User < ActiveRecord::Base
  belongs_to: subdomain
end

The factories are as follows:

FactoryGirl.define do
  factory :subdomain do
    name 'test-subdomain'
  end
  factory :user do
    subdomain
    email 'test-user@example.com'
    password '123456¿
    password_confirmation '123456'
  end
end

When I try to create two users using the following code:

FactoryGirl.create(:user, :email => "first@example.com")
FactoryGirl.create(:user, :email => "second@example.com")

I get the following error:

Validation failed: Name has already been taken (ActiveRecord::RecordInvalid)

This happens because when the first user is created, the default subdomain is created too and when the second user is created the subdomain already exists.

If we want to use the same subdomain for both users we can do the following:

s = FactoryGirl.create(:subdomain)
FactoryGirl.create(:user, :email => "first@example.com", :subdomain => s)
FactoryGirl.create(:user, :email => "second@example.com", :subdomain => s)

However as our has_many relations become deeper, test data creation becomes more complex.

My solution to this problem is as to change the factory for user:

factory :user do
  subdomain { Subdomain.find_by_name('test-subdomain') || FactoryGirl.create(:subdomain) }
  email 'test-user@example.com'
  password '123456'
  password_confirmation '123456'
end

In this case the factory uses the default subdomain if it already exists, avoiding the validation problem.

Now if we use the initial code, it works without problem, assigning both users to the default subdomain

FactoryGirl.create(:user, :email => "first@example.com")
FactoryGirl.create(:user, :email => "second@example.com")

However this does not limit us to use the same subdomain for all users:

other_subdomain = FactoryGirl.create(:subdomain, :name => "other-subdomain")

FactoryGirl.create(:user, :email => "first@example.com", :subdomain => other_subdomain)
FactoryGirl.create(:user, :email => "second@example.com")

In this case, the first user is assigned to other-subdomain and the second user is assigned to test-subdomain.

Processing previously uploaded files with paperclip

2010-09-28T00:00:00+00:00

It seems that the most popular use of paperclip is to upload and process images. However it is also very useful to handle data files.

I am currently using paperclip to upload data files and process them later in a background task using delayed_job since the files are quite big and proccessing them takes several minutes.

The problem is to access the file contents after it has been uploaded, the solution is to use the to_file method as shown in the following code fragment.

class UploadedFile < ActiveRecord::Base
  has_attached_file :pipes_file
 
  def process
    # Get the file contents
    content = self.pipes_file.to_file
    content.rewind
    while line = content.gets
      data = line.split "|"
      # do something with data
    end
  end
end

I am succesfully using this method in an app running on Heroku to process files uploaded to Amazon S3.

How to install Rails 3 on Ubuntu

2010-09-10T00:00:00+00:00

In this post you will find the steps to install the Ruby on Rails development environment on Ubuntu 10.04.

Install and configure git
Install rvm
Install ruby using rvm
Install rails
Create and test a rails app
Create your project’s rvm file

Install and configure git

$ sudo apt-get install git-core
$ git config --global user.name "Your name"
$ git config --global user.email your_email

If you want git’s graphical interfaces install

$ sudo apt-get install gitk
$ sudo apt-get install git-gui

Install rvm

$ sudo apt-get install curl
$ bash < <( curl http://rvm.beginrescueend.com/releases/rvm-install-head )

Edit .bashrc

Change the line that contains

[ -z "$PS1" ] && return

near the beginning of the file to

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

Indent all the remaining lines of the file and add a line containing

fi

at the end of the file.

Add another line at the end (after fi) containing

[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm"

and save your .bashrc file.

Close the terminal, open a new one and type

$ type rvm | head -n1

(number one, not letter l)

If everything is working you should see

rvm is a function

Note: After installing rvm do not use sudo to install gems.

Install ruby using rvm

Install the following packages required to build ruby:

$ sudo apt-get install build-essential bison openssl libreadline5 libreadline-dev zlib1g zlib1g-dev libssl-dev libsqlite3-0 libsqlite3-dev sqlite3 libreadline-dev libxml2-dev

the list of packages was obtained by typing

$ rvm notes

Install the required ruby version and select it. In my case I will install only Ruby Enterprise Edition

$ rvm install ree
$ rvm use ree

Create a gemset and select it

$ rvm gemset create mygemset
$ rvm gemset use mygemset

Install rails

$ gem install rails -v 3.0.0

Create and test a rails app

$ gem install sqlite3-ruby
$ rails new myproject
$ cd myproject
$ rails generate scaffold User name:string
$ rake db:migrate
$ rails server

In your browser navigate to http://localhost:3000, you should see the default rails page.

Navigate to http://localhost:3000/users and play with your new app creating, editing and erasing users.

Create your project's rvm file

$ echo "rvm ree@mygemset" >> .rvmrc

Image links in markdown

2010-03-18T00:00:00+00:00

I wanted to use an image from Flickr and give attribution to the creator, linking the image to its original location.

Since markdown supports inline html my first approach was to paste the following code in the markdown file:

<a href="http://link_url">
    <img src="http://image_url" />
</a>

However this approach is not elegant enough, it would be better if this could be done using pure markdown syntax.

The syntax for a link in markdown is:

[text](http://link_url)

And the syntax for an image in markdown is:

![alt text](http://image_url)

To create an image link in markdown the following could be used

[![alt text](http://image_url)](http://link_url]

There is an alternative method to create links and images in markdown, known as reference-style links, using IDs that refer to URLs later in the file. This is a neater syntax and allows us to keep all the URLs in one place, usually at the end of the file.

The reference-style syntax for a link is:

[text][id_1]

[id_1]: http://link_url

The reference-style for an image is

![alt text][id_2]

[id_2]: http://image_url

Finally, the resulting image link is:

[![alt text][id_2]][id_1]

[id_1]: http://link_url
[id_2]: http://image_url

Using rails-sqlserver-2000-2005-adapter on Windows

2009-02-27T00:00:00+00:00

This is a different approach to my previous post Using SQL Server in Rails 2

Now I am using Rails 2.2.2 on Windows and the Rails SQL Server 2000-2005 adapter. Additionally I am using ODBC, because ADO support seems to be deprecated.

The installation is straightforward as explained on the adapter’s github page:

gem install dbi --version 0.4.0
gem install dbd-odbc --version 0.2.4
gem install rails-sqlserver-2000-2005-adapter -s http://gems.github.com

Since we are using ODBC it is necessary to configure the data source using the ODBC Data Source Administrator in Windows Administrative Tools. In my case I used a System DSN.

The config\database.yml should look like this:

# Configuration for rails-sqlserver-2000-2005-adapter
# using ODBC

development:
  adapter: sqlserver
  mode: ODBC
  dsn: your_database_dsn
  username: your_sqlserver_user
  password: your_sqlserver_password

Where your_database_dsn is the System Data Source name that you defined in the ODBC Data Source Administrator.

Using SQL Server in Rails 2

2008-02-12T00:00:00+00:00

These are the steps to access a SQL Server database from a Rails 2.0 application running on Windows.

The SQL Server adapter is not incuded by default in Rails 2. It is necessary to download and install it using the following command.

gem install activerecord-sqlserver-adapter --source=http://gems.rubyonrails.org

Download the latest version of ruby-dbi from

http://rubyforge.org/projects/ruby-dbi/

and then extract the file from ruby-dbi\lib\dbd\ADO.rb to C:\ruby\lib\ruby\site_ruby\1.8\DBD\ADO\ADO.rb.

Warning, the folder ADO does not exist, so you have to create it in advance.

It is not possible to preconfigure rails for SQL Server using the –database option, just create your application as usual and then modify config\database.yml in your application folder as follows:

development:
  adapter: sqlserver
  database: your_database_name
  host: your_sqlserver_host
  username: your_sqlserver_user
  password: your_sqlserver_password

Run

rake db:migrate

to check your installation. If everything is fine you should not receive any error message.