Ruby bindings for Sundown, a fast and full-featured Markdown parser that lets you define renders for arbitrary output formats.

Guide to writing CLI scripts in Ruby that play nice with pipe chains.

When internationalizing your Rails app, you'll be replacing strings like 'Please enter your name' with t('.name_prompt'). You will be adding keys to your config/locales/*.yml files over and over again. Not to miss any key and place each at the right place is a challenging task.

The gem i18n-tasks has you covered. See its README for a list of things it will do for you.

Note

The i18n-tasks gem does not understand aliases and will duplicate all referenced data when it writes locales. If yo...

When Rack::Bug has been added to your project and your Apache2/Passenger only replies with an Error 500 (Internal Server Error) you won't get any love from both application and Apache logs.

You can start a script/server and try connecting there. It should also fail but you will most likely see this error:

Internal Server Error  
undefined method `new' for "Rack::Bug":String

While the following is (for some reason) working on OSX...

config.middleware.use "Rack::Bug", :secret_key => '...'

...you need to do this so it wor...

Framework to write command-line apps in Ruby. Comes with a nice way of processing parameter options, some utility classes and Cucumber steps for testing your CLI app.

[1,2,3,4].sample
# => e.g. 4

If you'd like to cheat and give different weights to each element in the array, you can use the attached initializer to say:

[1,2,3,4].weighted_sample([1,1,1,1000])
# => probably 4

When you use one line Ruby comments in ERB templates you should never do this (notice the whitespace in front of #):

<% # my comment %>

<div>my html</div>

This leads to strange html output. To avoid long debugging sessions, you should never have a whitespace before the # character (but newline is allowed)

<%# this works as expected %>

<%
    # this works, too
    # foo bar baz
%>

Seems like a useful gem for cases where ActiveRecord is overkill but you don't want to do everything by hand either.

Gem to generate entity relationship diagrams from your Rails 3 ActiveRecord models. The diagram style is pretty and configurable.

For performance improvements (and to remove the need for eager loading), the ActsAsTaggableOn gem supports caching your tag lists directly in your model. To enable this, simply add a cached_tag_list column to your table.

Example:

class Company < ActiveRecord::Base
  acts_as_taggable_on :categories
end

The cache column has to be named cached_category_list.

Existing data

If you already have existing data, you have to save all records with tags once, after you've added the ...

I still see people promoting various gems and plugins to handle miscellaneous configuration elements for your application. One little known secret is that Rails 3 allows you to define your own configuration elements trivially.

To use different Ruby versions on your computer you can use the Ruby Version Manager. It also allows you to pack different gemsets for each of your applications. In order to create on of those just type ...

rvm use 1.8.7-p323@makandra_project_xy --create

This command creates and switches to the newly created gemset.

"Classic" Excel (XLS) has a magic limit of 65535 rows per worksheet. This was fixed in XLSX but the version used by the Spreadsheet gem can only write XLS files.

If you want to write more data, consider hacking around it using in_groups_of and writing multiple column sets of your data (i.e. split 1 block of 3 columns and 100000 rows into 4 blocks of 3 (12 in total) columns and 25000 rows).

You can do this until you reach the other limit of 256 columns. After that, open up a new workbook or consider a ...

When you have objects in your database that hold latitude and longitude and you want to find others that are close to given coordinates you can use the Graticule gem.

Graticule

Graticule offers several methods to compute the distance between two geo-dated objects but fetching records from the database that are within a given radius of a location is a bit trickier:

def close_destinations(latitude, longitude)
  distance_sql = Graticule::Distance::Spherical.to_sql(:latitude => l...

ActiveSupport's memoize has a dangerous feature you might not know about.

Assume you have

class DeepThought
  extend ActiveSupport::Memoizable

  def life_universe_and_everything
     # some lengthy calculation returning 42
  end
  memoize :life_universe_and_everything
end

Then #life_universe_and_everything will of course cache the result after calculating it once. However, you can trigger a recalculation by calling #life_universe_and_everything(true).

If, however, your method looks like

de...

This is easy:

require 'open-uri'

File.open('/target/path/to/downloaded.file', "wb") do |file|
  file.write open('http://example.com/your.file').read
end

Basic Authentication

When your file is protected by HTTP Basic Authentication, pass your credentials as hash:

File.open('/target/path/to/downloaded.file', "wb") do |file|
  file.write open('http://example.com/your.file', :http_basic_authentication => [your_username, your_password]).read
end

There are several options, but most of them are impractical. The best way is to use the :ruby filter:

:ruby
  puts javascript_include_tag(
    'lib/jquery-1.6.1.min.js',
    'lib/jquery-rails-ujs.js',
    'lib/jquery-ui-1.8.13.custom.min.js',
    'lib/jquery.ui.datepicker-de.js',
    'lib/jquery-ui-timepicker-addon.min.js',
    'lib/jquery.tools.min.js',
    'application.js',
    'google-maps.js',
    :cache => true
  )

...

If you get an error like this:

Unable to launch /home/bruce/Projects/myproject/tmp/capybara/capybara-201110311210111407691101.html 

... update your launchy gem. It failed for us in version 0.4.x. We could fix the issue by upgrading to 2.0.5.

After starting the Rails server in a freshly generated Rails 3.1 project you could see an error message such as

/usr/lib/ruby/gems/1.8/gems/execjs-1.3.0/lib/execjs/runtimes.rb:50:in `autodetect': Could not find a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of available runtimes. (ExecJS::RuntimeUnavailable)

Just add a JavaScript runtime to your Gemfile and the error vanishes.

Examples:

gem 'therubyracer'
gem 'extjs'

Note: This applies specifically to MySQL. In PostgreSQL for example, this is not an issue.

If you care about performance, never use a query like

UPDATE users SET has_message = 1 WHERE users.id IN (SELECT user_id FROM messages)

MySQL does not optimize this and seems to scan the temporary table, which isn't indexed, for every row in the update statement. This applies to other statements than UPDATE as well.

Instead, either use a JOIN like

UPDATE users INNER JOIN messages ON messages.user_id = users.id SET has_message =...

Clearance is a gem that provides authentication functionality (e.g. login, logout). This note explains, how the clearance login, logout and (in old Clearances) remember me functionality works.

Login

Clearance defines a database column called "remember_token". When you login in, that token will be saved in a cookie. For that reason you don't have to re-sign-in when you close and open the browser again.
This also means that you can be logged in in more than a single browser. Also see [When ses...

By default, Rails views escape HTML in any strings you insert. If you want to insert HTML verbatim, you need to call #html_safe. However, #html_safe does not "unescape" a string. It merely marks a string as safe for unescaped insertion.

How html_safe works

Calling html_safe on a String returns a new object that looks and acts like a String, but actually is a ActiveSupport::SafeBuffer:

"foo".length
# => 3
"foo".class
# => String

"foo".html_safe.length
# => 3
"foo".html_safe.class
# => ActiveSupport::S...

If you encounter the error message above when running cucumber, just execute...
rm rerun.txt
...in the Rails directory.

Or run...
tests
...from the geordi gem. This will do the work for you automatically.

While 2.0 will include a number of syntax changes, new features and general improvements, mentioned below, it is anticipated to remain backward compatible with code written for 1.9.3 and Matz has stated that the changes are less significant than those made in the 1.8 to 1.9 jump.