MongoMapper is a MongoDB adapter for Ruby. We've forked it so it works for Rails 2.3.x applications running on Ruby 1.9. [1]

makandra/mongomapper is based on the "official" rails2 branch [2] which contains commits that were added after 0.8.6 was released. Tests are fully passing on our fork for Ruby 1.8.7, REE, and Ruby 1.9.3.

To use it, add this to your Gemfile:

gem 'mongo_mapper', :git => 'git://github.com/makandra/mongomapper.git', :branch => 'rails2'

...

Ruby 1.9 changed the default behavior of Module.const_defined? from what it was in Ruby 1.8 -- this can be especially painful when external code (read: gems) uses const_defined? to look something up and gets different results on different Rubies.

Consider this:

module Foo
  FOO = 42
end

class Bar
  include Foo
end

On Ruby 1.8, Bar won't have FOO defined as a constant since that's (even though it's accessible):

1.8.7 > Foo.const_defined? :F...

This error can happen in Ruby 1.9.

To fix it, add the following line to the top of your .js.erb file:

<%# @encoding: UTF-8 %>

Rails 2.3.16+ on Ruby 1.9 causes warnings like this:

.../gems/activesupport-2.3.17/lib/active_support/core_ext/string/output_safety.rb:22: warning: regexp match /.../n against to UTF-8 string

Many thanks to grosser for supplying a monkey-patch for Rails 2.3 (Commit f93e3f0ec3 fixed it for Rails 3). Just put it into config/initializers/ to make those warnings go away.

Since we're using RSpec on mos...

So you have a method returning a regular expression but one case that should not yield a matching Regexp object but still keep the API stable? Just return one that never matches:

/(?!)/

You either have an old version of Mocha and an edge version of Rails 3.2, or you have a new version of Mocha and an old version of Rails. The best solution is to update Mocha to the latest version and switch to Rails edge.

If you are using shoulda-matchers or another gem that locks Mocha to an old version, you are out of luck.
More info with many other workarounds that you do not want to use can be found here. A hack to work around this case is to add the following file to lib/mocha/setup.rb:...

Stringex is a gem that offers some extensions to Ruby's String class. Ruby 1.9 compatible, and knows its way around unicode and fancy characters.

Examples for stringex's String#to_url method:

# A simple prelude
"simple English".to_url => "simple-english"
"it's nothing at all".to_url => "its-nothing-at-all"
"rock & roll".to_url => "rock-and-roll"

# Let's show off
"$12 worth of Ruby power".to_url => "12-dollars-worth-of-ruby-power"
"10% off if you act now".to_url => "10-percent-off-if-you-act-now"

# You do...

UnicodeUtils implements Unicode algorithms for case conversion, normalization, text segmentation and more in pure Ruby code.

If you don't need the ton of features that UnicodeUtils offers, try stringex.

RVM needs to be updated regularly to know of Ruby versions released since installation (or last update).

So if you say rvm install 1.9.3, but get an old version (basically anything below 1.9.3-p385 when writing this card), your RVM is outdated. \
Fix that by saying:

rvm get stable

After that, rvm install 1.9.3 should install the latest 1.9.3 version.

If bundle install shows the following message for you ...

Error Bundler::HTTPError during request to dependency API

... upgrade to Bundler ≥ 1.2.4:

gem install bundler

Apparently, it just hides the message.

In our continued quest to extract proven code snippets from makandropedia into tested and upgradable gems, we have released Edge Rider.

Edge Rider was created with two intents:

1. Provides a number of utility methods to facilitate hardcore work with scopes.
2. Provide a stable API for working with scopes across multiple versions of Rails, since Rails has a tradition of breaking details of its scope API every other release.

The gem bundles multiple patches and initializers we've been using for hard...

The Edge Rider gem gives your relations a method #traverse_association which
returns a new relation by "pivoting" around a named association.

Say we have a Post model and each Post belongs to an author:

class Post < ActiveRecord::Base
  belongs_to :author
end

To turn a relation of posts into a relation of its authors:

posts = Post.where(:archived => false)
authors = posts.traverse_association(:author)

You can traverse multiple associations in a single call.
E....

TLDR: Ruby class variables (@@foo) are dangerous in many ways. You should avoid them at all cost. See bottom of this card for alternatives.

Class variables are shared between a class hierarchy

When you declare a class variable, it is shared between this and all descending (inheriting) classes. This is rarely what you want.

Class variables are bound at compile-time

Like unqualified constants, class variables are bound to your current scope *whe...

This works well in the simplified case, when your link disappears after it was clicked.

Let link_to_remote behave as „disabled“ after the first click. Use the :before hook to replace the orignal link with a link that does nothing but looks like the original link:

:ruby
  label = "do_something"
  dummy_link = link_to(label)
  other_attributes_hash = { :url => ..., :method => ..., ... }
  
  disable_link_option = { :before => "$('your_link_selector').html('#{escape_javascript(dummy_link)}'" } # jquery

= link_to_remote(label, other_att...

Ruby has two different ways to match the start and the end of a text:

• ^ (Start of line) and $ (End of line)
• \A (Start of string) and \z (End of string)

Most often you want to use \A and \z.

Here is a short example in which we want to validate the content type of a file attachment. Normally we would not expect content_type_1 to be a valid content type with the used regular expression image\/(jpeg|png). But as ^ and $ will match lines, it matches both content_type_1 and content_type_2. Using \A and \z will wo...

January has been a very bad month for Ruby on Rails developers, with two high-severity security bugs permitting remote code execution found in the framework and a separate-but-related compromise on rubygems.org, a community resource which virtually all Ruby on Rails developers sit downstream of. Many startups use Ruby on Rails. Other startups don’t but, like the Rails community, may one day find themselves asking What Do We Do When Apocalyptically Bad Things Happen On Our Framework of Choice? I thought I’d explain that for the general c...

The problem

Calling bundle update GEMNAME will update a lot more gems than you think. E.g. when you do this:

bundle update cucumber-rails

... you might think this will only update cucumber-rails. But it actually updates cucumber-rails and all of its dependencies. This will explode in your face when one of these dependencies release a new version with breaking API changes. Which is all the time.

In the example above updating cucumber-rails will give you Capybara 2.0 (because capybara is a dependency of `cucumber-rail...

Calling bundle update (without arguments) updates all your gems at once. Given that many gems don't care about stable APIs, this might break your application in a million ways.

To stay sane, update your gems using the applicable way below:

Projects in active development

Update the entire bundle regularily (e.g. once a week). This ensures that your libraries are up-to-date while it's easy to spot major version bumps which may break the app.

Projects that have not been updated in a while

1. [Update a single gem conservatively](htt...

If you worked with a system Ruby before switching to RVM, this system Ruby will be in your way when you switch between projects with/without RVM.

It's hard to get rid of your system Ruby entirely, but you can tell RVM to just use a given Ruby by default, e.g.:

rvm --default use 1.8.7

You need to re-open existing terminals for the changes to take effect.

Note that this will not actually remove the ruby package from your system, it just isn't used anymore.

If you use Tempfile and pass your own filename containing an extension, it will just be consumed by the Tempfile's filename:

>> Tempfile.new('foobar.xlsx').path
=> "/tmp/foobar.xlsx20130115-19153-4ykpwm-0"

If you want to keep the file extension, pass filename and extension as an array:

>> Tempfile.new([ 'foobar', '.xlsx' ]).path
=> "/tmp/foobar20130115-19153-1xhbncb-0.xlsx"

Use Socket.gethostname. So for a machine whose hostname is "happycat", it will look like this:

>> Socket.gethostname
=> "happycat"

That should work right away for your Rails application. For plain Ruby, you first need to do:

require 'socket'

If you don't want to use Socket for some reason, you can still just use the hostname command, at least on non-Windows machines. Keep in mind that you need to remove trailing white space from the result of the system call.

>> `hostname`
=> "happycat\n"
>> `hostname`.stri...

Upgrade the offending gem. If you cannot or don't want to upgrade, lock rake to 0.8.7.

While you are probably using will_paginate to paginate ActiveRecord scopes, it can actually paginate plain Ruby arrays. The resulting arrayish object will have the same methods as a paginated scope, e.g. #total_entries. This means you can render pagination controls with the same code that works with paginated scopes.

To enable this, add an initializer config/initializers/array_paginate.rb:

require 'will_paginate/array'

You can now say:

> numbers = (1..1000).to_a
> page = numbers....

With the impending release of Ruby on Rails 4, it looks like a lot of developers will be updating their web applications in the coming new year.

To help with this transition, over the next 31 days, we are going to be releasing a series of blog posts going over everything you will need to know about Rails 4 for an effortless upgrade.