When using ActionMailer, you can set an array of email addresses as recipients. If this array is generated by e.g. collecting email addresses from the database, it might sometimes be empty.

To prevent ActionMailer to deliver mails to nobody, simply overwrite the deliver! method like this:

# In your mailer.rb
def deliver!(mail = @mail)
  return false if (recipients.nil? || recipients.empty?) && (cc.nil? || cc.empty?) && (bcc.nil? || bcc.empty?)
  super
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...

Sometimes you can make your life easier by not allowing a record attribute to be changed after the record was created. An example for this is when your model represents a child node in a composition and has logic that is hard to support for cases when the container changes.

Here is an example for a container Region composed of many children of type Holiday. After saving a Holiday it caches the current number of holidays in its region:

class Region < ActiveRecord::Base

...

ActiveRecord comes with a method touch which sets the updated_at timestamp to the current time. Unfortunately it also runs callbacks (and hence validations) on the receiving record, so it is unsuitable if you call it very often.

Use the attached initializer to get a touch_gently method which updates updated_at, but does not run callbacks:

User.find(5).touch_gently

The initializer will also give you a method touch_all_gently whi...

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, `...

Sometimes you need to dynamically load an image and do something as soon as its loaded (when for example its size is already available).

With jQuery, this seems to work across browsers:

$('<img>')
  .attr('src', '')
  .load(function() {
    alert('fully loaded!');
  })
  .attr('src', '/the/real/image/url');

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...

Add deprecation warnings and their solution or link to available solutions.

Global access to Rake DSL methods is deprecated. Please include Rake::DSL into classes and modules which use the Rake DSL methods.

Open your Rakefile and add the following line above YourApp::Application.load_tasks:

YourApp::Application.class_eval do
  include Rake::DSL
end

Use of ole/file_system is deprecated. Use ole/storage (the file_system api is recommended and enabled by default)...

Pie sometimes does not properly redraw elements upon changes. This often happens when the change comes from somewhere further up the DOM.

Consider something like:

<ul>
  <li class="active"><div class="content">Active element</div></li>
  <li class="inactive"><div class="content">Inactive element</div></li>
</ul>

with CSS
li .content {
-webkit-box-shadow: #666 0px 2px 3px;
-moz-box-shadow: #666 0px 2px 3px;
box-shadow: #666 0px 2px 3px;
behavior: url(/PIE.htc);

  back...

JavaScript Garden is a growing collection of documentation about the most quirky parts of the JavaScript programming language. It gives advice to avoid common mistakes, subtle bugs, as well as performance issues and bad practices that non-expert JavaScript programmers may encounter on their endeavours into the depths of the language.

JavaScript Garden does not aim to teach you JavaScript. Former knowledge of the language is strongly recommended in order to understand the topics covered in this guide

The attached RSpec matcher exist_in_database checks if a given record still exists in the database and has not been destroyed:

describe Ticket do
  describe '.purge_expired' do
    fresh_ticket = Ticket.create(:expiry => Date.tomorrow)
    expired_ticket = Ticket.create(:expiry => Date.yesterday)
    Ticket.purge_expired
    fresh_ticket.should exist_in_database
    expired_ticket.should_not exist_in_database
  end
end

Note that there is also [ActiveRecord::Base#destroyed?](http://apidock.com/rails/ActiveRecord/Base/destroyed...

When you need to insert many records into the same table, performance may become an issue.

What you can do to save time is to open a transaction and save multiple records within that transaction:

transaction do
  500.times { Model.create! }
end

Although you will still trigger 500 INSERT statements, they will complete considerably faster.

When I tried it out with a simple model and 500 iterations, the loop completed in 1.5 seconds vs. 6 seconds without a transaction.

Alternative

Another fast way to insert many ...

Depending on where you live, different rules are used to determine the number of the week and a weekday. You have no chance whatsoever to get this right globally unless you make it your life's purpose. However, when you work for clients from Europe or the US, there are two dominantish standards you should know about. Each of these has subtle differences.

ISO 8601

• This is adhered to by most European countries.
• Weeks start on Mon...

You can find ActiveRecord models by using a Range as its conditions:

User.scoped(:conditions => { :id => 3..5 })

This will generate the following query:

SELECT * FROM `users` WHERE (`users`.`id` BETWEEN 3 AND 5)

This also means that all your scopes that take an array of allowed values and use condition hashes, automagically work for Ranges, too.

In order to

• track down warnings and to see failing specs immediately
• or to get an overview of the core functionalities,

you can use RSpec's "nested" format. It looks like this:

Tool
  validations
    should require model to be set
    should require place_id to be set
  #identifier
    should include the model and tag if the tool has a tag
    should return the model if the tool has no tag
  .search
    should find tools by model and maker
    should find tools by serial number

Call RSpec like...

You will occasionally need to clean out your database while keeping the schema intact, e.g. when someone inserted data in a migration or when you had to kill -9 a frozen test process.

Old Capybara versions already have the Database Cleaner gem as dependency. Otherwise add database_cleaner to your *Gemfile`. This lets you say this from the Rails console:

DatabaseCleaner.strategy = :truncation
DatabaseCleaner.cl...

When you click a link or a press a button on a Selenium-controlled browser, the call will return control to your test before the next page is loaded. This can lead to concurrency issues when a Cucumber step involves a Selenium action and a Ruby call which both change the same resources.

Take the following step which signs in a user through the browser UI and then sets a flag on the user that was just signed in:

Given /^the user "([^"]*)" signed in (\d) days ago$/ do |name, days|
  visit new_session_path
  fill_in 'Username', :w...

When you set both a record's association and that association's foreign key attribute, Rails does not realize you are talking about the same thing. The association change will win in the next save, even if the foreign key attribute was changed after the association.

As an example, assume you have these two models:

class Group < ActiveRecord::Base
  has_many :users
end

class User < ActiveRecord::Base
  validates_presence_of :group_id
  belongs_to :group
end

We will now load a User and change both its `g...

Note: For PostgreSQL you should use advisory locks. For MySQL we still recommend the solution in this card.

If you need to synchronize multiple rails processes, you need some shared resource that can be used as a mutex. One option is to simply use your existing (MySQL) database.

The attached code provides a database-based model level mutex for MySQL. You use it by simply calling

Lock.acquire('string to synchronize on') do
  # non-th...

Issue

When you have a Cucumber step like

Then I should see "Did you see those \"quotation marks\" over there?"

you'll run into trouble. Cucumber won't take your escaped quotation marks.

Workarounds

One workaround is to write the step as regex (since there is a step taking a regex):

Then I should see /Did you see those "quotation marks" over there\?/

Keep in mind it’s a regex – escape regex characters like '?'.

When you have a Cucumber step like

Then I should fill in "query" with "\"some phrase\""

The fo...

On 32bit systems, the maximum representable Time is 2038-01-19 03:14:07 in UTC or 2038-01-19 04:14:07 in CET. If you try to instantiate a Time with any later value, Ruby will raise an ArgumentError.

If you need to represent later time values, use the DateTime class. This is also what Rails does when it loads a record from the database that has a DATETIME value which Time cannot represent. Note that there are some [subtle differences](http://stackoverflow.com/quest...

This tool is used on our application servers (and called when deploying) but it also works locally.
Just call dumple development from your project directory to dump your database.

This script is part of our geordi gem on github.

The code below shows a method #validate which uses Nokogiri to validate an XML document against an XSD schema. It returns an array of Nokogiri::XML::SyntaxError objects.

require 'rubygems'
gem 'nokogiri'
require 'nokogiri'

def validate(document_path, schema_path, root_element)
  schema = Nokogiri::XML::Schema(File.read(schema_path))
  document = Nokogiri::XML(File.read(document_path))
  schema.validate(document.xpath("//#{root_element}").to_s)
end

v...