Do not try to "slice" on an ActionController::CookieJar

The cookies object in your controllers and views is a ActionController::CookieJar and even though that class inherits from Hash and often behaves like one, you can not call slice on it to select only a subset of cookies. Why? Because Hash#slice calls self.class.new -- which in case of a CookieJar just won't work.

Unfortunately, you can't even say cookies.to_hash and slice on that, just because CookieJar#to_hash is inherited from Hash and will just return self. Bummer.

You need to do it yourself, for example by usin...

Bash: How to generate a random number within given boundaries

$RANDOM on bash returns a random integer between 0 and 32767.

echo $RANDOM
9816
echo $RANDOM
30922

If you want to limit that to a certain maximum, you can just compare against the modulus of that maximum + 1. \
For example, the following will yield results between 0 and 9:

echo $(($RANDOM % 10))
5
echo $(($RANDOM % 10))
9

Note that this skews random numbers to the lower regions of your boundaries in most cases.

ActionView::Template::Error (dump format error for symbol(0x6d))

I recently encountered the error above when I was running selenium tests.

Thanks to a post on stackoverflow I found out that clearing all files in tmp/cache in my project folder made the issue go away.

Sprites with Compass

Using CSS sprites for background images is a technique for optimizing page load time by combining smaller images into a larger image sprite.

There are ongoing arguments on how useful this still is, as modern browsers become more comfortable to load images in parallel. However, many major websites still use them, for example amazon, [facebook](...

Switch to a recently opened tab with Cucumber

Similar to closing an opened browser window, spreewald now supports the I switch to the new browser tab step.

Info

See the Spreewald README for more cool features.

You can use it to test links that were opened with a link_to(..., :target => '_blank') link or other ways that create new tabs or windows.

Important

This only works with Selenium ...

Live CSS / view reloading

Next time you have to do more than trivial CSS changes on a project, you probably want to have live CSS reloading, so every time you safe your css, the browser updates automatically. It's pretty easy to set up and will safe you a lot of time in the long run. It will also instantly reload changes to your html views.

Simply follow the instructions below, taken from blog.55minutes.com.

Install CSS live reload (only once per project)

  1. Add th...

Howto remove the location hash without causing the page to scroll

Set the hash to a dummy hash which doesn't hit any id at your page, for example:

window.location.hash = "_";

Note

  • If you'd set the hash to "" it causes the page to scroll to the top because the hash "#" by itself is equivalent to "_top".
  • If you'd set window.location.href = "..." to get rid of the "#", you cause the browser to reload the page what is most likely not intended.

Common mistakes when storing file uploads with Rails

1. Saving files to a directory that is not shared between deploys or servers

If you save your uploads to a made up directory like "RAILS_ROOT/uploads", this directory goes away after every deploy (since every release gets a new). Also this directory is not shared between multiple application servers, so your uploads are randomly saved to one local filesystem or another. Fixing this afterwards is a lot of fun.

Only two folders are, by default, shared between our application servers and deployments: "RAILS_ROOT/storage" and `"RAILS...

Upgrading Rails 2 from 2.3.8 through 2.3.18 to Rails LTS

This card shows how to upgrade a Rails 2 application from Rails 2.3.8 through every single patch level up to 2.3.18, and then, hopefully, Rails LTS.

2.3.8 to 2.3.9

This release has many minor changes and fixes to prepare your application for Rails 3.

Step-by-step upgrade instructions:

  1. Upgrade rails gem
  2. Change your environment.rb so it says RAILS_GEM_VERSION = '2.3.9'
  3. Change your ...

ActiveRecord.select

Active Record's select method allows you to make use of the power of MySQL select statements. On the one hand it allows you to select specific fields.

Post.select("content")

results in the following query:

"SELECT content FROM `posts`"

This means that your models will be initialized with only the content attribute and you will not be able to access any other attribute. In fact trying so would raise an ActiveRecord::MissingAttributeError error.

 Post.select("content").first.title # => ActiveRecord::MissingAttributeErr...

Help me, there is a zombie process!

Here is a good explanation for zombie processes.

Quote:

If you have zombie processes it means those zombies have not been waited for by their parent (look at PPID displayed by ps -l). 
You have three choices: Fix the parent process (make it wait); kill the parent; or live with it.
Remember that living with it is not so hard because zombies take up little more than one extra line in the output of ps.

On a server I want to get informed if there are zombie processes and track them wi...

Before you make a merge request: Checklist for common mistakes

Merge requests are often rejected for similar reasons.

To avoid this, before you send a merge request, please confirm that your code ...

Subscribe to Rails security mailing list without Google account

The Ruby on Rails security list archive can be found here: http://groups.google.com/group/rubyonrails-security

You can subscribe to this mailing list without a Google account by pasting this URL into your browser (after replacing the email address obviously).

http://groups.google.com/group/rubyonrails-security/boxsubscribe?email=your.name@example.com
                                                                       ^^^^^^^^^^^^^^^^^^^^^ <- Change this

News flash: Absolute CSS positioning on opposite sides is not a problem

Back in the old days, we couldn't do something like that:

.foo {
  position: absolute;
  bottom: 0;
  /* This was bad: */
  left: 10px;
  right: 10px;
}

Why? Because IE5 and IE6 (which a majority of people used back then) failed horribly trying to render it.

I've now checked if this is still an issue with any browser that's not from the stone age. \
Turns out all is well -- except if you have to support IE6 and below, but then you're in some other kinds of trouble.

It works in all sane browsers, and Internet Explorer 7, 8...

How to clear cookies in Capybara tests (both Selenium and Rack::Test)

Capybara drivers will usually delete all cookies after each scenario. If you need to lose cookie data in the middle of a scenario, you can do this:

browser = Capybara.current_session.driver.browser
if browser.respond_to?(:clear_cookies)
  # Rack::MockSession
  browser.clear_cookies
elsif browser.respond_to?(:manage) and browser.manage.respond_to?(:delete_all_cookies)
  # Selenium::WebDriver
  browser.manage.delete_all_cookies
else
  raise "Don't know how to clear cookies. Weird driver?"
end

Duplicate a git repository with all branches and tags

In order to clone a git repository including all branches and tags you need to use two parameters when cloning the old and pushing to the new repository respectively:

git clone --bare http://example.com/old-repo.git
cd old-repo
git push --mirror http://example.com/new-repo.git

Of course, the URLs to your repository might look different depending on the protocol used, username required, etc.
For a user git using the git protocol, it could be git@example.com:repository-namespace/repository.git

How to find out which type of Spec you are

When you need to find out in which kind of spec you are during run-time, it's definitely possible. It's a lot easier in RSpec 2+.

For example, consider this global before block where you'd want to run some code for specific specs only:

config.before do
  # stuff
  that_fancy_method
  # more stuff
end

RSpec 2+

If you want to run such a block for a specific type of specs, you can use filters:

config.before do
  # stuff
  # more stuff
end

config.before :type =...

How to find out if you are in Cucumber or in RSpec

Sometimes you need a piece of code to do something different for specs than for features. If you don't have separate environments, you can't check your Rails.env.

I managed to distinguish between specs and features by asking Capybara.

Note that this only works when you do not use Capybara in specs.

if defined?(Capybara) and Capybara.respond_to?(:current_driver)
  # you're in a Cucumber scenario
else
  # you're probably in a spec
end

You could omit the defined?(Capybara) condition, if you are sure that Capybara...

Browsers will not send a referrer when linking from HTTPS to HTTP

  • When your site is on HTTPS and you are linking or redirecting to a HTTP site, the browser will not send a referrer.
  • This means the target site will see your traffic as "direct traffic", i.e. they cannot distinguish such hits from a user who directly typed in the URL.

Reasons for this behavior

It's probably because of this RFC:

Clients SHOULD NOT include a Referer header field in a (non-secure) HTTP request if the referring page was transferr...

Quick git contributors list

git shortlog -s -n [commit-range]

-n, --numbered
Sort output according to the number of commits per author

-s, --summary
Suppress commit descriptions, only provide commit count

[commit-range]
E.g. $tagname.. for "everything after that tag"

Example output for spreewald:

60  Tobias Kraze
12  Henning Koch
 7  Dominik Schöler
 6  Thomas Eisenbarth
 5  Martin Straub
 3  Minh Hemmer
 2  Alex McHale
 1  Manuel Kallenbach
 1  Andreas Robecke

#...

Good real world example for form models / presenters in Rails

We have often felt the pain where our models need to serve too many masters. E.g. we are adding a lot of logic and callbacks for a particular form screen, but then the model becomes a pain in tests, where all those callbacks just get in the way. Or we have different forms for the same model but they need to behave very differently (e.g. admin user form vs. public sign up form).

There are many approaches that promise help. They have many names: DCI, presenters, exhibits, form models, view models, etc.

Unfortunately most of these approaches ...

Pitfall: ActiveRecord callbacks: Method call with multiple conditions

In the following example the method update_offices_people_count won't be called when office_id changes, because it gets overwritten by the second line:

after_save :update_offices_people_count, :if => :office_id_changed? # is overwritten …
after_save :update_offices_people_count, :if => :trashed_changed? # … by this line

Instead write:

after_save :update_offices_people_count, :if => :office_people_count_needs_update?

private

def office_people_count_needs_update?
  office_id_changed? || trashed_changed?
end

Or...

OpenStack instance not configuring network (DHCP) correctly

We ran into trouble when adding additional compute units to our railscomplete Hosting environment lately.

VM-instances on the new compute units where booting and requesting private IP addresses via DHCP correctly (DHCPDiscover), but after the answer of the dnsmasq dhcp server (DHCPOffer) we did not see any further traffic on the host machine. FYI: The instance should request the IP via DHCPRequest which in turn should be acknowledged by a DHCPAcknowledgment packet.

We assumed this DHCP UDP traffic did not...

How to discard a surrounding Bundler environment

tl;dr: Ruby's Bundler environment is passed on to system calls, which may not be what you may want as it changes gem and binary lookup. Use Bundler.with_original_env to restore the environment's state before Bundler was launched. Do this whenever you want to execute shell commands inside other bundles.

Example outline

Consider this setup:

my_project/Gemfile     # says: gem 'rails', '~> 3.0.0'
my_project/foo/Gemfile # says: gem 'rails', '~> 3.2.0'

And, just to confirm this, these are the installed Rails versions for each ...