Deadlocks only occur if two transactions in separate threads compete for the same rows in the database. They usually (but not necessarily) only happen when trying to update or otherwise lock several rows in different order.

Solving deadlocks is potentially complicated, so here are a few pointers:

• MySQL should always detect the deadlock right when it happens, and will throw an error to one of the offending threads. This error states the SQL statement that this thread was currently waiting for, and that tried to acquire one of the competin...

If your controller spec never reaches your controller code:

1. Make sure you are signed in.

2. Make sure you are actually triggering a request by saying get :edit or something siliar.

3. Know that views are not rendered by default for controller specs unless you tell them to (render_views).
   ^
   describe UsersController do
   describe '#edit' do
   it 'should work' do
   sign_in
   get :edit
   end
   end
   end

   define something like this in your spec_helper.rb:

   def sign_in(user = User....

When a has_many association basically serves to store a list of associated strings (tags, categories, ...), it can be convenient to represent this association as a string array in the containing model. Here is an example for this pattern from the acts-as-taggable-on gem:

post = Post.last
p post.tag_list # ['foo', 'bar', 'baz']
post.tag_list = ['bam']
p post.tag_list # ['bam']

This string array tag_list is magical in several ways:

• It is read from and written to a `has...

When you just went through a long debug-fest and infested your code with dozens of debug messages, it can be hard to find all those calls to puts and p. This note describes a hack that lets you trace those messages in your code.

Let's say you want to get rid of a console message "foobar". Copy the Undebug class below to config/initializers.rb. In the same initializer, type a line:

Undebug.trace_message('foobar')

Now run tests or whatever you need to do to to trigger that message. The console output should look like this:

...

Occasionally some complex query must be processed on the database because building thousands of Ruby objects is impracticable.

Many times you would use scope options, like this:

users = User.scoped(
  :joins => 'INNER JOIN orders joined_orders ON users.id = joined_orders.user_id',
  :conditions => [ 'joined_orders.date BETWEEN ? AND ?', start_date, end_date ],
  :select => '*, SUM(joined_orders.amount) AS amount_sum',
  :group => 'users.id'
)

You get ActiveRecord objects and you can ask each of them about its `amou...

Plugins (and gems) are typically tested using a complete sample rails application that lives in the spec folder of the plugin. If your gem is supposed to work with multiple versions of Rails, you might want to use to separate apps - one for each rails version.

For best practice examples that give you full coverage with minimal repitition of code, check out our gems has_defaults and assignable_values. In particular, take a look at:

• Multiple `sp...

For clarity and traceability, your commit messages should include the ID and title of the Pivotal Tracker story you're working on. For example:

[#12345] Add Google Maps to user profiles
Optional further commit messages in the body

Also see Howto: Write a proper git commit message

To quickly generate such commit messages, add a new link "Commit" to your bookmarks and use the following Javascript as the link URL:

javascript:(function() { ...

The following initializer provides an :alias => "my_route_name" option to restful routes in your route.rb. This simply makes the same route also available under a different ..._path / ..._url helpers.

For example,

map.resources :notes, :alias => :snippets

Gives you

notes_path, notes_url, new_note_path... #as always
snippets_path, snippets_url, new_snippet_path... #from the alias

Put this into an initializer:

This note describes a Cucumber step definition that lets you test whether or not a CSS selector is present on the site:

Then I should see an element "#sign_in"
But I should not see an element "#sign_out"

Here is the step definition for Capybara:

Then /^I should (not )?see an element "([^"]*)"$/ do |negate, selector|
  expectation = negate ? :should_not : :should
  page.send(expectation, have_css(selector))
end

Here is the step definition for Webrat:

Then /^I should (not )?see an element "([^"]*)"$/ do |negate...

If a controller action responds to other formats than HTML (XML, PDF, Excel, JSON, ...), you can reach that code in a controller spec like this:

describe UsersController do
  describe '#index' do
    it 'should be able to send an excel file' do
       # stubs and expectations go here
       get :index, :format => 'xls'
    end
  end
end

Remember that both the :format parameter and the HTTP_ACCEPT header can m...

You will need to upgrade to RSpec >= 2 and rspec-rails >= 2 for Rails 3. Here are some hints to get started:

• In RSpec 2 the executable is rspec, not spec.
• RSpec and rspec-rails have been completely refactored internally. All RSpec classes have been renamed from Spec::Something to RSpec::Something. This also means that every require 'spec/something' must now be require 'rspec/something'.
• In spec_helper.rb, Spec::Runner.configure becomes RSpec.configure
• It has become really hard to extend specific example groups ...

If you previously used version 2.x of Thunderbird and upgraded to 3.x (for example through an Ubuntu release upgrade) you might notice that Thunderbird will not show any of your old e-mails or settings.

This results from a different directory being used for storing profiles and configuration.

You can replace the blank profile with your old one like this:
cd ~
mv .thunderbird .thunderbird-invalid
cp -R .mozilla-thunderbird .thunderbird

Upon its next start, Thunderbird brings up the migration wizard introducing you to a few vers...

If you did file operations inside a shell or for example using Nautilus, it can take quite a while until RubyMine takes note of them and updates things like your project tree or its internal file list.

Flushing file system buffers helps you out (run it from a terminal):
sync

This is also possibly via the RubyMine menus: File → Synchronize.

Take care when trying to set attributes to nil in a blueprint.

Given the following master blueprint:
Story.blueprint do
title
author { User.make }
editor { User.make }
end

This approach will not overwrite/remove the editor defined in the master blueprint:
Story.blueprint(:draft) do
editor nil
end

...whereas this one will (note the lambda):
Story.blueprint(:draft) do
editor { nil }
end

Sometimes the order in which strings appear on a page matters to you.

Spreewald gives you steps like these:

Then I should see in this order:
  | Alpha Group |
  | Augsburg    |
  | Berlin      |
  | Beta Group  |

Or, if you prefer multiline strings:

Then I should see in this order:
  """
  Alpha Group
  Augsburg
  Berlin
  Beta Group
  """

The step ignores all HTML tags and only tests on plain text.

Note: We are talking about Machinist 1 here, Machinist 2 may have solved this or might require a different approach.

Machinist allows named blueprints (e.g. User.blueprint(:admin)) that inherit from the master blueprint (User.blueprint).

If you also want to inherit from another blueprint (e.g. if "vip" should load "premium" and the master blueprint) you can do this:
User.blueprint(:vip) do
# Fields for the vip blueprint go her...

If you want to see how long your database queries actually take, you need to disable MySQL's query cache. This can be done globally by logging into a database console, run

SET GLOBAL query_cache_type=OFF;

and restart your rails server.

You can also disable the cache on a per query basis by saying

SELECT SQL_NO_CACHE * FROM ...

You also probably want to disable Rails internal (per-request) cache. For this, wrap your code with a call to ActiveRecord::Base.uncached. For example, as an around_filter:

d...

Even when you're using bundler, it might be significant in which order your gems are listed in your Gemfile. This can happen when gems are running around calling require or require_dependency on other gems or application classes when loaded (don't do that!).

A known culprit of this is the (otherwise wonderful) resource_controller gem, which requires ApplicationController when loaded. When your ApplicationController requires later-loaded gems when loaded, Rails will not boot.

He...

Inside before :each blocks you can refer to variables that you introduce via let later on.

They do not need to be defined ahead of your before block and can be different for individual sections.

It works just like that:

describe User do
  describe '#locked?' do
    
    before :each do
      subject.should_receive(:current_plan).and_return plan
    end
    
    context 'when expiring today' do
      let(:plan) { stub(:expiry => Date.today) }
      it 'should be false' do
        subject....

If a SSH shell dies (from timeout for example), you cannot kill it with the usual CTRL-C or CTRL-Z. Instead, press
[ENTER]~.
(That is ENTER TILDE PERIOD).

These steps are now part of Spreewald.

This note describes a Cucumber step that lets you write this:

Then I should see a table with the following rows:
  | Bruce Wayne       | Employee    | 1972 |
  | Harleen Quinzel   | HR          | 1982 |
  | Alfred Pennyworth | Engineering | 1943 |

If there are additional columns or rows in the table that are not explicitely expected, the step won't complain. It does however expect the rows to be ordered as stat...