Capybara gives you two different methods for executing Javascript:

page.evaluate_script("$('input').focus()")
page.execute_script("$('input').focus()")

While you can use both, the first line (with evaluate_script) might freeze your browser window for 10 seconds.

The reason is that evaluate_script will always return a result. The return value will be converted back to Ruby objects, which in case of complex objects (e.g. a jQuery collection) is very expensive.

Because of this we recommend to only use evaluate_script whe...

Rarely, you might want to rebuild all gems with native extensions, because they might be compiled against outdated system libraries, resulting in some warnings or even segfaults or other ruby errors.

You can do that using

gem pristine --all

This will reset all gems to a pristine state as if you'd reinstall them, and as a side effect, rebuild all native extensions.

The above command will also help you sorting out errors like this after a distribution upgrade:

libmysqlclient_r.so.16: cannot open shared object file: No such fil...

url = 'http://www.foocorp.com/foo/bar'
URI.parse(url).host
# => www.foocorp.com

Note that this will raise an error if the given argument is not a URL.

If you need the host's full URL without path, query, fragment etc., use URI.join with a clever twist:

url = 'http://www.foocorp.com:33546/foo/bar?query=foobar#hash'
URI.join url, '/'
# => http://www.foocorp.com:33546/

In theory you can take any scope and extend it with additional joins or conditions. We call this chaining scopes.

In practice chaining becomes problematic when scope chains grow more complex. In particular having JOINs in your scope will reduce the scope's ability to be chained with additional JOINs without crashes or side effects. This is because ActiveRecord doesn't really "understand" your scope chain, it only mashes together strings that mostly happen to look like a MySQL query in the end.

**I don't generally advice against u...

In a nutshell:

If you require your Rails models manually, pay attention to the path you use. Unless you have to, don't do it at all.

Background

Consider these classes:

# app/models/user.rb

class User < ActiveRecord::Base
  validate :magic

  def magic
    errors.add_to_base('failed') if bad_things?
  end
end

^
# app/models/foo.rb

require 'user'

class Foo
  # something happens here
end

Now, when your environment is booted, Rails will automatically load your models, like User...

The (admittedly crazy) goal of this Gem is to be able to format/split all phone numbers in the world.

This is for you if you get the following strange error from the state_machine gem:

undefined method `-' for #<StateMachine::BlacklistMatcher:0x124769b0>

You probably did something like this in your state_machine ... do block:

def self.final_states
  [ :foo, :bar ]
end

transition (all - machine.final_states - [:baz]) => :target_state

Instead, define the source states like this:

def self.final_states
  [ :foo, :bar ]
end

transition (all - (mach...

The linked slidedeck holds many tips, of which I list the most interesting to me below

DATA and END

The __END__ keyword tells Ruby where a file ends – but you don't have to stop there. Any text you add after it is accessible via the DATA object.

Running the attached example file data.rb prints:

DATA is a File object to everything in the current file after "__END__"

No braces needed for 'special variables'

@instance, @@class, $global = [ 'instance', 'class', 'global' ]
puts "#@instance, #@@class, #$global"

...

The __END__ keyword tells Ruby where a file ends – but you don't have to stop there. Any text you add after it is accessible via the DATA object.

The attached example file data.rb looks like this:

puts DATA.read

__END__
DATA is a File object to everything in the current file after "__END__"

Running it with ruby data.rb prints:

DATA is a File object to everything in the current file after "__END__"

Ruby's mathn library changes Fixnum division to work with exact Rationals, so

2 / 3 => 0
2 / 3 * 3  => 0

require 'mathn'
2 / 3 => Rational(2,3)
2 / 3 * 3 => 2

While this might sometimes be quite neat, it's a nightmare if this gets required by some gem that suddenly redefines integer division across your whole project. Known culprits are the otherwise excellent distribution and [GetText](https://g...

If you get this warning on your local machine one of these steps might help:

Rebuilt the gem with the newer library

gem install --no-rdoc --no-ri nokogiri -- --with-xml2-include=/opt/local/include/libxml2 --with-xml2-lib=/opt/local/lib

If you still get the error, try to uninstall all nokogiri versions with

gem uninstall nokogiri

and install nokogiri again.

Fixing the issue on servers

However, on our servers this probably will not work. On the server, gems are stored in the ../shared/bundle/ruby/:version/gems dire...

If some of your JavaScripts fail on Internet Explorer, but only in staging or production environments, chances are that JavaScript compression is the culprit.

By default, Rails 3.2 compresses JavaScript with UglifyJS. I have seen a few cases where this actually breaks functioning JavaScript on IE (one example is the CKEditor).

I fixed this by switching to Yahoo's YUI Compressor.

To do this, do the following:

• replace the uglifier gem with the yui-compressor gem...

This describes how to migrate an existing cucumber test suite to Spreewald.

0. Add the gem

1. Include spreewald into your cucumber environment by putting
   require 'spreewald/web_steps'
   require 'spreewald/email_steps'
   # ...
   or just
   require 'spreewald/all_steps'
   into your support/env.rb.

2. Look through your step definitions for everything that might be included in Spreewald. Candidates are web_steps, shared_steps, table_steps, `em...

Cucumber_rails' old-school web-steps have been deprecated for a while, urging developers to write high-level step definitions that directly use Capybara or Webrat.

We think that's a bit drastic. More high-level steps are good, but ticking the odd check box with a general step is not always bad.

So we took the old web steps, improved them a bit, added some other favorites of ours (steps for emails, tables, [time travelling](/ma...

The ActionMailer in Rails 2 depends on a buggy version of TMail, which sometimes inserts a blank line into the mail header when sending a mail to multiple recipients. This makes the header end prematurely.

The reason why this is not exploding in your face all the time is that when you are relaying your e-mail through an MTA like Exim, it will fix this for you.

Fix for Rails if you don't have an awesome MTA

TMail is no longer maintained. The bug is fixed...

Simply use OpenStruct#to_h to receive an OpenStruct's hash representation.
In older Rubies you need OpenStruct#marshal_dump instead.

Ruby 2.0+

>> OpenStruct.new(foo: 23, bar: 42).to_h
=> { :foo => 23, :bar => 42 }

Ruby 1.9.3 and 1.8.7

>> OpenStruct.new(:foo => 23, :bar => 42).marshal_dump
=> { :foo => 23, :bar => 42 }

Both approaches will return the underlying hash table (a clone of it in Ruby 2.0+).

Ever wanted autocompletion for paths from paths.rb in Cucumber? This card lets you write your steps like this:

When I go to path *press tab now* # path is replaced with a list of all known Cucumber paths

This is how you do it

(key shortcuts apply for TextMate2)

1. Open the bundle editor (ctrl + alt +  + B)

2. Create a new Item ( + N), select "Command"

3. Paste this:
   ^
   #!/usr/bin/env ruby -wKU
   require File.join(ENV['TM_SUPPORT_PATH'], 'lib', 'ui.rb')

   cucumber_paths = File.join ENV['TM_PROJECT_DIRECTORY'], 'features'...

When you get an error like this:

Invalid gemspec in [/opt/www/foo-project.makandra.de/shared/bundle/ruby/1.8/specifications/carrierwave-0.6.2.gemspec]: Illformed requirement ["#<YAML::Syck::DefaultKey:0x7fda6f84d2e8> 1.1.4"]

... the machine's Rubygems needs to be updated.

If that happens on your local machine

• Manually remove the offending's gem files and specifications. The paths will be something like /usr/lib/ruby/gems/1.8/gems/your-broken-gem and `/usr/lib/ruby/gems/1.8/specificatio...

We frequently use the handy Paperclip Gem to manage file attachments.

If you need to move the files from local storage (i.e., your servers' harddisk) to Amazon S3, you can simply change settings for Paperclip to use the S3 storage adapter and use this script to migrate to S3. Put the snippet into a chore if you don't want to run that in the console.
YOUR_LOCAL_STORAGE_MODEL_DIRECTORY should be something like 'storage/your_model'.

Dir.glob(YOUR_LOCAL_STORAGE_MODEL_DIRECTORY**/*).each do |path|...

If you have an html_safe string, you won't be able to call gsub with a block and match reference variables like $1. They will be nil inside the block where you define replacements (as you already know).

This issue applies to both Rails 2 (with rails_xss) as well as Rails 3 applications.

Here is a fix to SafeBuffer#gsub. Note that it will only fix the $1 behavior, not give you a safe string in the end (see below).

Example

def test(input)...

In a nutshell: return statements inside blocks cause a method's return value to change. This is by design (and probably not even new to you, see below) -- but can be a problem, for example for the capture method of Rails.

Consider these methods:

def stuff
  puts 'yielding...'
  yield
  puts 'yielded.'
  true
end

We can call our stuff method with a block to yield. It works like t...

If you get errors from your development WEBrick that contain unicode salad, you are probably requesting the page via SSL. \
Since WEBrick does not speak SSL, so change the URL in your browser to use http instead of https.

The error looked like this for me:

[2012-09-06 11:19:07] ERROR bad URI `\000\026\000\020\000'.
[2012-09-06 11:19:07] ERROR bad URI `\000\026\000\020\000'.
[2012-09-06 11:19:07] ERROR bad Request-Line `\026\003\001\000�\001\000\000\177\003\001PHj�\031\006�L��'.
[2012-09-06 11:19:07] ERROR bad URI `\000\026\000\...