Whenever is a Ruby gem that provides a clear syntax for writing and deploying cron jobs.

Validations that need to access an associated object may lead to some trouble. Let's exemplify that using this example:

class Project < ActiveRecord::Base
   has_one :note
end

class Note < ActiveRecord::Base
   belongs_to :project
end

Now say we need a validation that ensures that a description is set (validates_presence_of :description) within Note but only if the Project has a flag called external set to true. The following code will lead to some problems as the associated object is not present when creatin...

When storing floating-point numbers such as prices or totals in an SQL database, always use a DECIMAL column. Never use FLOAT or kittens will die.

DECIMAL columns are parametrized with a precision and a scale. These parameters describe which numbers can be stored in that column. E.g. a decimal with a precision of 5 and a scale of 2 can store numbers from -999.99 to 999.99, but not 1000 or 1.234.

This card explains what various databases do when you try to store a number in a DECIMAL field, and that number exceeds that colum...

Sass now comes with user-defined functions, keyword arguments, list manipulation. Haml and Sass are now two separate gems.

The Edge Rider gem will define a method collect_ids on your ActiveRecord models, scopes, integer scalars and collections, which will return a list of their IDs:

User.last.collect_ids # => [9]
[User.first, User.last].collect_ids # => [1, 9]
User.active.collect_ids # => [4, 5, 6]
[4, 5, 6].collect_ids # => [4, 5, 6]
7.collect_ids #=> [7]

This allows you to parametrize scopes with a variety of argument types:

class Note < ActiveRecord::Base
  named_scope :for_users, lamb...

A capybara driver that uses WebKit via QtWebKit.

Our new scope-based authorization gem for Ruby on Rails has been released. This might one day replace Aegis as our standard authorization solution.

Documentation for the horrible RDoc syntax.

If you want to convert a README.rdoc file to HTML, say this from a shell:

rdoc README.rdoc

You will find the generated HTML in doc/index.html.

If you do this while working on one of our gems, please .gitignore everything in doc and don't commit the generated HTML.

Ruby gem to check whether a given bic/account-no-combination can possibly be valid for a German bank. Can also resolve German bank names from a given bic.

If you are using RVM on a Mac and cannot enter 8+ bit characters on an IRB or Rails console, you are missing the readline package. You will need to re-install your Ruby to fix this:

rvm remove ree
rvm package install readline
rvm install ree --with-readline-dir=$rvm_path/usr
rvm default ree

Substitute ree with the name if your Ruby distribution.

This note was contributed by Matthias Marschall from the Agile Web Development & Operations blog.

• Reading a URL via GET:

  curl http://example.com/
  

• Defining any HTTP method (like POST or PUT):

  curl http://example.com/users/1 -XPUT
  

• Sending data with a request:

  curl http://example.com/users -d"first_name=Bruce&last_name=Wayne"
  

  If you use -d and do not set an HTTP request method it automatically defaults to POST.

• Performing basic authentication:

  curl http://user:password@example.com/users/1
  

• All together now:

  curl http://user:password@example.com/users/1 -XPUT -d"screen_name=batman"
  

...

Rails 3

User.active.to_sql

Rails 2

Use either the Edge Rider or fake_arel gem to get #to_sql backported to Rails 2.

If you don't want to use a gem for this, you can do this with vanilla Rails 2:

User.active.construct_finder_sql({})

Since version 1.5 RubyGems requires at least Ruby 1.8.7. The last one working with Ruby 1.8.6 was RubyGems 1.4.2.

You get still download it from their servers and install RubyGems.

When installing RMagick you may get an error messages like this:

Version 2.13.1:

checking for Ruby version >= 1.8.5... yes
checking for gcc... yes
checking for Magick-config... no
Can't install RMagick 2.13.1. Can't find Magick-config in /home/arne/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/var/lib/gems/1.8/bin

*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
d...

Artifice allows you to replace the Net::HTTP subsystem of Ruby with an equivalent that routes all requests to a Rack application.

You can use Sinatra, raw Rack, or even Rails as your application, allowing you to build up an equivalent to the remote service you are mocking out using familiar and convenient tools to route requests and build up responses.

Phillip Koebbe from Ruby on Rails suggested inserting following code between the "bootstrap" and "initialize" sections of enviroment.rb. This hack fixes the problem.

if Gem::VERSION >= "1.3.6"
  module Rails
    class GemDependency
      def requirement
        r = super
        (r == Gem::Requirement.default) ? nil : r
      end
    end
  end
end

The information in this card is only relevant for Rails 2.3-era apps.

This note gives a quick introduction into caching methods (page caching, action caching and fragment caching) in rails and describes some specific problems and solutions.

The descriptions below are valid for Rails 2 and 3. Recently, caching with timestamp- or content-based keys has become more popular which saves you the pain of invalidating stale caches.

How to enable/disable caching

To enable or disable caching in rails you ca...

Note that you cannot currently use Ruby 1.9.2 with Rails 2 applications that use RSpec, so don't upgrade if that is your setup. The rspec-rails gem has a fatal bug that was only fixed for rspec-rails-2.x, which only supports Rails 3. There is no fix for the rspec-rails-1.3.x series of the gem which supports Rails 2.

Anyway, here are upgrade instructions if you only work with Rails 3 or don't use RSpec. You will lose all your gems in the process, but you can get them back easily if you h...

List of global variables available to a Ruby script.

Specify these gem versions in your Gemfile:

gem 'cucumber', '~> 1.3.0'
gem 'cucumber-rails', '= 0.3.2' # max version for Rails 2
gem 'capybara', '< 2' # capybara 2+ requires Rails 3
gem 'mime-types', '< 2' # dependeny of capybara
gem 'nokogiri', '< 1.6' # dependency of capybara
gem 'rubyzip', '< 1' # dependency of selenium-webdriver, rubyzip 1+ requires Ruby 1.9
gem 'cucumber_factory'
gem 'database_cleaner', '< 1'
gem 'cucumber_spinner', '~> 0.2.5'
gem 'launchy', '~> 2.1.2'

With these versions set, `...

The shell variable PS1 holds your bash prompt. You might want to change it to serve your needs best. Here is how to:

General

• non-printing escape sequences in your prompt have to be inclosed in \[\e[ and \] so your shell can correctly count its prompt's length
• we recommend to highlight your prompt on production machines
• you can also [show different root prompts for each user](https://makandracards.com/makandra/9569-get-the-username-w...

Now allows to list transition paths from and to arbitrary states.