git diff commit_hash -- path/to/file

Provide any commit hashes or branch names like "master" for commit_hash.

To install webmock 1.5.0:

sudo gem install webmock --version "=1.5.0"

or
sudo gem install webmock -v "=1.5.0"

As a user of Bundler you have spent significant time looking at this message:

Fetching source index for http://rubygems.org/

To make Bundler skip this index update and only use installed gems, you can use the --local option:

bundle install --local

Unfortunately this does not work with bundle update.

It is said that Bundler 1.1 will use a feature of Rubygems.org that allows partial index updates. Hopefully the wh...

Regular spaces and non-breaking spaces are hard to distinguish for a human.
Instead of using the   HTML entity or code like " " # this is an nbsp, use a well-named helper method instead.

def nbsp
  [160].pack('U*')
end

160 is the ASCII character code of a non-breaking space.

Given this class:

class Foo
  class Bar
  end
end

If you want to clean up this code with the modularity gem, you might try something like this:

class Foo
  does 'bar'
end

module BarTrait
  as_trait do
    class Bar
    end
  end
end

Note that this changes Bar's full class name from Foo::Bar to BarTrait::Bar. If you have methods inside Foo (or other classes), you would have to change all references accordingly, which is quite unpleasant.

You can solve it like that:
`...

This is a bash script for those of you who need to install all gems for all projects (e.g. to get started quickly on a newly installed system).

Put it into your ~/bin/ and run it from the directory that holds your projects.

Note that, like the vanilla bundle install, this will fail whenever a new gem compiles native components and requires a missing system dependency.

Use this scope:

class Stick
  named_scope :shuffled, lambda {
    last_record = last
    { :conditions => [ 'id >= ?', rand(last_record.id) ] } if last_record
  }
end

You can now pick a random stick by saying

Stick.shuffled.first

Or, if you prefer something smaller:

class Stick
  named_scope :shuffled, :order => 'RAND()'
end

Note however that you should never order by RAND() on tables that may become large some day, as this performs horribly and can kill your database server.

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...

• Ctrl + R Search commands you entered previously. Press Ctrl + R again to search further back, Ctrl + Shift + R searches forward again.

• Ctrl + W Deletes from the cursor position to the left.

• Ctrl + _ Undo. Yes, this also works with a German keyboard layout.

• Ctrl + L Clear screen.

• Ctrl + D _Close shell. (EOT, just like in many other shells.) Note: if you dove into another shell (e.g. with sudo su username) you will close it and return to ...

Compresses JavaScript.

Thanks to habits engrained by Rails 2’s link_to_remote and remote_form_for, we expect that Rails 3 would also handle the AJAX response for our remote links and forms. But it doesn’t; it leaves that for you.

This note describes how to setup a box running Ubuntu to share its Internet connection with another PC.

• You will need two network interfaces to do this. One will connect to the Internet (e.g. UMTS card), one will share the connection with the other PC (e.g. Wired LAN).
• On the Ubuntu PC, right-click on the connection symbol in the tray. Select Edit connections.
• Switch to the wired LAN card. Go to Edit and set the method to Shared to other computers.
• Connect the other PC to your wired LAN card. You can use the same cable that wo...

Terminus is a Capybara driver where most of the driver functions are implemented in client-side JavaScript. It lets you script any browser on any machine using the Capybara API, without any browser plugins or extensions.

Sometimes you inherit a non Rails or non Rack based web app such as PHP, Perl, Java / JEE, etc. I like using cucumber for functional testing so I put together this project structure to use as a starting point for testing non Ruby web based applications.

Use this MySQL command to show further info about a table:

SHOW CREATE TABLE tags;

This will output a table schema like this:

CREATE TABLE `tags` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `index_tags_on_name` (`name`)
) ENGINE=InnoDB AUTO_INCREMENT=60 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci

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 can now add an :inverse_of option to has_one, has_many and belongs_to associations.... Without :inverse_of m and f.man would be different instances of the same object (f.man being pulled from the database again). With these new :inverse_of options m and f.man are the same in memory instance.

When doing a presentation you may want to hide your desktop icons.

You can switch them off (or back on) like this:

• Open up gconf-editor
• Navigate to apps -> nautilus -> preferences
• (Un)check "show_desktop"

After switching to Rails 3 you may get a LoadError with the following message when trying to use your application via passenger:
no such file to load -- dispatcher

Your Passenger version is most likely out of date.

Update the gem, then install the apache module again:
sudo gem install passenger
sudo passenger-install-apache2-module

Follow any instructions. Update your /etc/apache2/httpd.conf with the lines given at the end of the installation process to use the version you just installed.

You might find that your Passenger ignores all RailsSomething directives in the vhost for your new Rails 3 application. The culprit is a file config.ru which makes Passenger consider your application a Rack (non-Rails) application.

To fix this you can either use RackEnv in lieu of RailsEnv (it works fine) or delete the config.ru. Unless you have a good reason to do so, go with RackEnv.

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 ...

Be careful when using params.merge as params is a HashWithIndifferentAccess.

Why?

Usually this should not be an issue but it turns crazy if you try to include associated models deeper than 1 level:
options = params.merge(:include => { :user => :avatar })
Post.paginate options

When inspecting the merged params you will get something like this:
{ :include=> { "user" => :avatar }, :page => 23 }

Here the :user symbol in the hash of inclusions turned into a "user"...

In rare cases you might need something like form_for (for using form builder methods on the resulting block element) but without the surrounding form. One such case would be updating some of a form's fields via XHR.

You can simply use Rails' fields_for to do things like this in your views (HAML here):

- fields_for @user do |form|
  = form.label :email, 'E-Mail'
  = form.text_field :email

You will only receive the form content you gave, no hidden inputs incl...