How to install mysql gem on Ubuntu 10.04

sudo apt-get install mysql-server mysql-client
sudo apt-get install libmysql-ruby libmysqlclient-dev
sudo gem install mysql

Install mysql database connector by running the above commands.

How to install Nokogiri on Ubuntu

libxml2 is missing error message is due to missing libraries. Install the pre-requisite library with:

sudo apt-get install libxslt-dev libxml2-dev

How to install curb gem on Ubuntu 10.04

sudo apt-get install libcurl3 libcurl3-gnutls libcurl4-openssl-dev

How to install bson_ext on Ubuntu 10.04

Using Bundler 1.1.3 for some reason does not work. Solution:

sudo gem install bson_ext -v=1.0.1

installs the gem.

How to ssh using a given private key

ssh -i /path/to/your_private_key_file user-name@your-ip-address-here

It is recommended that your private key files are NOT accessible by others

I was getting this error : Permissions 0644 for '/home/bparanj/Downloads/my-file.ssh' are too open.
when I was ssh ing into a box.

Solution:

sudo chmod 600 your-private-key.ssh

Rails Recipes 3rd Edition

The recipe: Focus Your Tests with Mocking and Stubbing show how to use stubs and mocks. It violates one of the testing best practices. DO NOT mock external services. Why? Because you cannot drive the design of a third party library. For a good discussion on this topic read the "Growing Object Oriented Software Guided by Tests".

I scanned through the book, I was a bit disappointed. Lot of the recipes are just from the old book.

WARNING: 'require 'rake/rdoctask'' is deprecated. Please use 'require 'rdoc/task' (in RDoc 2.4.2+)' instead. WARNING: 'require 'rake/rdoctask'' is deprecated. Please use 'require 'rdoc/task' (in RDoc 2.4.2+)' instead

Include rdoc in the Gemfile :

group :development, :test do
  gem 'rcov'
  gem "rdoc", '~> 3.12'
end

Run bundle install.

Using Stubs with Test Spy in Ruby

While I was working on my super stealth product of my company - Affiliate Tracking system, I came across a problem during testing. I had to test the cookie setting logic of my controllers. It was straightforward to test that the cookie was set for the happy path. For the alternative scenario it became tricky to test because RSpec and Rails framework did not play that well together. I even read Devise Rails plugin code to see how Jose Valim handled cookie related problems during testing. No luck. One solution I found was on Stackoverflow. How do I test cookie expiry?

# app/controllers/widget_controller.rb
...
def index
    cookies[:expiring_cookie] = { :value   => 'All that we see or seem...', 
                                  :expires => 1.hour.from_now }
end
...
# spec/controllers/widget_controller_spec.rb
...
it "sets the cookie" do
  get :index
  response.cookies['expiring_cookie'].should eq('All that we see or seem...')
                                               # is but a dream within a dream.
                                               #                - Edgar Allan Poe
end

it "sets the cookie expiration" do
  stub_cookie_jar = HashWithIndifferentAccess.new
  controller.stub(:cookies) { stub_cookie_jar }

  get :index
  expiring_cookie = stub_cookie_jar['expiring_cookie']
  expiring_cookie[:expires].to_i.should be_within(1).of(1.hour.from_now.to_i)
end

This technique is a great example of Test Spy described in Gerard Mezos book xUnit Test Patterns. Basically, you install a spy and check the results collected by the test spy in the verification phase. In this case the Hash is the Test Spy that collects data. See how the stub is used to install the spy in the SUT? It overcomes the problems and isolates the SUT from the Rails framework and allows the code to be tested easily.

In my TDD bootcamps, the topic on Stubs and Mocks generates lot of discussion. To clear confusion that surrounds the stubs and mocks, I would state : Read Martin Fowler's paper on Mocks Aren't Stubs, Stub can never fail your test, only mocks can fail your test. Using stubs in combination with a spy like this makes stubs seem like they can in fact fail your test. But only the data collected by the Test Spy decides whether the test passes or not. So the stub's main purpose is to just isolate the production code from Rails framework and allow access to the internal state of the SUT where there is no direct way to access it.

TDD Bootcamp Videos

You can watch the TDD Bootcamp videos on YouTube. It is over 5.5 hours of recording.

Testing and Command Query Separation Principle

The term 'command query separation' was coined by Bertrand Meyer in his book "Object Oriented Software Construction".

The fundamental idea is that we should divide an object's methods into two categories:

    Queries: Return a result and do not change the observable state of the system (are free of side effects).
    Commands: Change the state of a system but do not return a value.

Because the term 'command' is widely used in other contexts it is referred as 'modifiers' and 'mutators'.

It's useful if you can clearly separate methods that change state from those that don't. This is because you can use queries in many situations with much more confidence, changing their order. You have to be careful with modifiers.

The return type is the give-away for the difference. It's a good convention because most of the time it works well. Consider iterating through a collection in Java: the next method both gives the next item in the collection and advances the iterator. It's preferable to separate advance and current methods.

 There are exceptions. Popping a stack is a good example of a modifier that modifies state. Meyer correctly says that you can avoid having this method, but it is a useful idiom. Follow this principle when you can.

From jMock home page: Tests are kept flexible when we follow this rule of thumb: Stub queries and expect commands, where a query is a method with no side effects that does nothing but query the state of an object and a command is a method with side effects that may, or may not, return a result. Of course, this rule does not hold all the time, but it's a useful starting point.

Stubs are not Mocks - Concise Version of Martin Fowler's Article

Stubs - a common helper to testing environments. There is a difference in how test results are verified: a distinction between state verification and behavior verification. Focusing on one element of the software at a time -hence the common term unit testing. The problem is that to make a single unit work, you often need other units.

• Dummy objects are passed around but never actually used. Usually they are just used to fill parameter lists.
• Fake objects actually have working implementations, but usually take some shortcut which makes them not suitable for production (an in memory database is a good example).
• Stubs provide canned answers to calls made during the test, usually not responding at all to anything outside what's programmed in for the test. Stubs may also record information about calls, such as an email gateway stub that remembers the messages it 'sent', or maybe only how many messages it 'sent'.
• Mocks are what we are talking about here: objects pre-programmed with expectations which form a specification of the calls they are expected to receive.

Only mocks insist upon behavior verification. The other doubles can, and usually do, use state verification.

The classical TDD style is to use real objects if possible and a double if it's awkward to use the real thing. A mockist TDD practitioner, however, will always use a mock for any object with interesting behavior.

An acknowledged issue with state-based verification is that it can lead to creating query methods only to support verification. It's never comfortable to add methods to the API of an object purely for testing, using behavior verification avoids that problem.

RCov Tips

1. How to turn off rcov for specific sections in a file:
Start and end with :

#:nocov:

in your file.

2. How to exclude files from rcov:

In spec directory, edit rcov.opts

 append our path of files to –exclude option. Eg: –exclude “helpers/*,app/sweepers/*”.

Reference

http://psixty.wordpress.com/2010/06/22/how-to-exclude-files-in-rcova-code-coverage-tool-in-ruby/

How to uninstall all gems in global rvm ?

rvm use @global 
rvm gemset empty global

If you want to remove all gems for a particular gemset, replace global with your-gemset-name

gem "rake" is not installed

Problem uninstalling rake? Run the following command:
rvm use @global && gem uninstall rake

How to disable acts_as_audited 2.0 rails plugin in Rails 3.1 and RSpec

Create disable.rb under spec/support folder and call disable_auditing method on your modes. For example:
Account.disable_auditing
Cart.disable_auditing

Using Reek gem in Rails 3.1 projects

1. gem install reek
2. reek lib/*.rb > myreport.txt

You can run reports for app/models/*.rb, app/controllers/*.rb and app/helpers/*.rb

rcov for Rails 3.1

1. rake spec:rcov
2. open coverage/index.html
3. add coverage/* to your .gitignore file.
4. $ rake -T rcov
rake spec:clobber_rcov  # Remove rcov products for rcov
rake spec:rcov          # Run all specs in spec directory with RCov (excluding plugin specs)

Rails Best Practices

1. gem install rails_best_practices
2. gem install ripper
3. From the root of the project run: 
rails_best_practices -f html .
to generate the report.

You need to specify gem names as Strings. Use 'gem "test"' instead.

This can happen due to syntax error in your Gemfile. Fix the sytax error by manually checking this file. If that does not work delete the lines that you added to result in this problem and copy / paste from a working copy of a Gemfile.

syntax error, unexpected keyword_end

This happens because you have : <%= end %> instead of <% end %>

`test': unknown command 't' (ArgumentError)

To write tests using Test::Unit new syntax :

test "truth" do
  assert true
end

1. gem install test-unit
2. Code:

require 'rubygems'
gem 'test-unit'
require 'test/unit'


class ExampleTest < Test::Unit::TestCase
  def test_truth
    assert true
  end
 
  test "truth" do
    assert true
  end
end


3. Run: ruby example_test This will work on ruby-1.9.3-p0.

Reference:  Test::Unit and MiniTest with different Ruby versions

Installing Ruby 1.9.3 using RVM on Mac OS Lion

ERROR: The provided CC(gcc) is LLVM based, it is not yet fully supported by ruby and gems, please read `rvm requirements`.

1) Download Xcode 4.2.x via App Store.
2) Go to Applications folder and click Install Xcode
3) Download and install GCC from https://github.com/kennethreitz/osx-gcc-installer
4) In a new terminal run : export CC=gcc
and then run : rvm install 1.9.3
5) You may also want to upgrade ruby gems by running:
gem update --system

ActiveRecord::Relation, undefined method error

If you are using the active record relationships to access columns, for instance:

Article has many comments
article.comments.where("spam = ?", false).order("created_at asc")

This returns ActiveRelation object that does not fire the query. Only when you loop through the results you can access the columns of comments objects. If you want to force the call to the database just append "all" to it like this:

article.comments.where("spam = ?", false).order("created_at asc").all

(local out of date) error in Git when working with branches

1. git pull origin your-branch
2. git push origin your-branch

Step 1 brings your local branch to up-to date. Step 2 pushes your changes to the remote branch.

invalid date format in specification: gem ruby

1) Upgraded ruby gems to 1.8.11 (gem update --system)
2) gem pristine --all

No luck.

Deleted all the gemspec that were causing problems: whenever-0.6.8.gemspec etc. Then bundle install made it work.

`build_extensions': ERROR: Failed to build gem native extension. (Gem::Installer::ExtensionBuildError)

I was getting :
Installing eventmachine (0.12.10) with native extensions .rvm/rubies/ruby-1.8.7-p330/lib/ruby/site_ruby/1.8/rubygems/installer.rb:533:in `build_extensions': ERROR: Failed to build gem native extension. (Gem::Installer::ExtensionBuildError)

during the installation of scheduler_daemon on Mac OS Lion. Upgraded XCode via appstore (download from appstore and install) to resolve this issue.

Integrating Tweet Button in Rails App

In Rails 3.0 app:

1) In Gemfile include:

gem 'tweet-button'

2) bundle install

3) In application_helper.rb include:

module ApplicationHelper
include TweetButton

... other methods...
end

4) In your partial:

<%= tweet_button(:via => "CreditCardLogic", :url => polymorphic_url(article), :text => "Check this out!") %>

To see this in action, check out my credit cards site.

Making a Branch the Master in GIT

git checkout cat_killer
git merge -s ours master
git checkout master
git merge cat_killer
git push

cat_killer is the branch you want to make the master.

Stolen from Stackoverflow post.

no mongrel gem found in sdk rubymine

Even if you are using RVM, Rubymine actually looks at the global installation for the gem. Install thin, mongrel etc on the global Ruby installation that is independent of any gemset.

How to start Thin server on a different port?

thin start -p 80

require that is compatible with ruby 1.8.x and 1.9.x

require File.expand_path(File.join(File.dirname(__FILE__), 'player'))

This makes : require 'player' work on both Ruby 1.8.x and 1.9.x

ImageMagick Installer

Download the script from https://github.com/maddox/magick-installer/blob/master/magick-installer.sh and run it.

ImageScience on Snow Leopard

1) Download and install MacPorts http://www.macports.org/install.php
2) sudo port install freeimage
3) env ARCHFLAGS="-arch x86_64" gem install RubyInline image_science

Reserved Words in Rails

To find out if a given name is reserved in Rails programmatically, check out this How to find out if a name is reserved in Rails 4.2.5.

* ADDITIONAL_LOAD_PATHS
* ARGF
* ARGV
* ActionController
* ActionView
* ActiveRecord
* ArgumentError
* Array
* BasicSocket
* Benchmark
* Bignum
* Binding
* CGI
* CGIMethods
* CROSS_COMPILING
* Class
* ClassInheritableAttributes
* Comparable
* ConditionVariable
* Config
* Continuation
* DRb
* DRbIdConv
* DRbObject
* DRbUndumped
* Data
* Date
* DateTime
* Delegater
* Delegator
* Digest
* Dir
* ENV
* EOFError
* ERB
* Enumerable
* Errno
* Exception
* FALSE
* FalseClass
* Fcntl
* File
* FileList
* FileTask
* FileTest
* FileUtils
* Fixnum
* Float
* FloatDomainError
* GC
* Gem
* GetoptLong
* Hash
* IO
* IOError
* IPSocket
* IPsocket
* IndexError
* Inflector
* Integer
* Interrupt
* Kernel
* LN_SUPPORTED
* LoadError
* LocalJumpError
* Logger
* Marshal
* MatchData
* MatchingData
* Math
* Method
* Module
* Mutex
* Mysql
* MysqlError
* MysqlField
* MysqlRes
* NIL
* NameError
* NilClass
* NoMemoryError
* NoMethodError
* NoWrite
* NotImplementedError
* Numeric
* OPT_TABLE
* Object
* ObjectSpace
* Observable
* Observer
* PGError
* PGconn
* PGlarge
* PGresult
* PLATFORM
* PStore
* ParseDate
* Precision
* Proc
* Process
* Queue
* RAKEVERSION
* RELEASE_DATE
* RUBY
* RUBY_PLATFORM
* RUBY_RELEASE_DATE
* RUBY_VERSION
* Rack
* Rake
* RakeApp
* RakeFileUtils
* Range
* RangeError
* Rational
* Regexp
* RegexpError
* Request
* RuntimeError
* STDERR
* STDIN
* STDOUT
* ScanError
* ScriptError
* SecurityError
* Signal
* SignalException
* SimpleDelegater
* SimpleDelegator
* Singleton
* SizedQueue
* Socket
* SocketError
* StandardError
* String
* StringScanner
* Struct
* Symbol
* SyntaxError
* SystemCallError
* SystemExit
* SystemStackError
* TCPServer
* TCPSocket
* TCPserver
* TCPsocket
* TOPLEVEL_BINDING
* TRUE
* Task
* Text
* Thread
* ThreadError
* ThreadGroup
* Time
* Transaction
* TrueClass
* TypeError
* UDPSocket
* UDPsocket
* UNIXServer
* UNIXSocket
* UNIXserver
* UNIXsocket
* UnboundMethod
* Url
* VERSION
* Verbose
* YAML
* ZeroDivisionError

Other names that have been reported to cause trouble:

* accept
* callback – breaks validation if used as a model method.
* categorie
* action
* attributes – if you have a has_many called attributes, you can’t access to your object attributes anymore; only the associated objects
* application2
* @base_path – setting this variable name in a controller method seems to break the ablity to render a partial in the view. The view will render with no content and no errors will be generated .
* connection – there seems to be a connection class already
* database – (in mysql)
* dispatcher
* display1
* drive – fixtures will not autogenerate IDs in Rails 2.0.2
* errors
* format
* host – I had a text_field :host, :name that I saw problems with. (JR)
* key
* layout – If you have a model called Layout and in a controller have “scaffold :layout” it generates an exception. However, if you script/generate the scaffold for layout it works.
* load – When making an Ajax call to an action named load, the action’s code will be skipped (or otherwise rendered useless). This is made apparent by: a) @variables are not available in the view, b) calling render :layout => false still yields the layout.
* link – breaks migrations when used as a column name in combination with validation: ticket
* new, override to news if you want a news table
* notify – not a valid column name
* open – not a valid column name
* public
* quote ‘quote’ cannot be used as a column name
* render – cannot be used as an action name
* request
* records – a table named records seemed to cause duplicate entries to be found by find
* responses – scaffold borks with "undefined method ‘body=’ "
* save – ActiveRecord uses this to save the object.
* scope – do not use as an association name because ActiveRecord::Base.scope is called instead
* send
* session (session_controller or SessionController will not work)
* system – a table column named system causes problems when trying to generate scaffold
* template – a table named templates causes an error when you try to invoke the create method of the default controller
* test (however those work with ruby test/unit/axistest.rb_ and rake testunits_)
* timeout – an ActiveRecord attribute named timeout will clash with the global function “timeout” defined in Ruby’s timeout.rb
* to_s — naming a model instance method to_s resulted in ‘File not found’ for any view an object of this class (should have) appeared in (no matter which method called) and WebRick had to be restarted. I couldn’t drag the very cause into light, but in the traces ‘to_s’ gave me a hint. After renaming everything worked well again.
* type — or any of the other MagicFieldNames
* URI
* visits — a table column named visits causes problems when trying to query some_obj.visits.
* Observer — for a model name works in development environment but not in production.
singular names finishing in “s”: Axis → Axes, Access → Accesses, will break the pluralization in rake: Axi, Acces

Monitor cannot be used. It is a Ruby class that is related to threading.

List of Magic Field Names

* created_at
* created_on
* updated_at
* updated_on
* lock_version
* type
* id
* #{table_name}_count
* position
* parent_id
* lft
* rgt
* quote_value (is used for quoting)
* template

uninstalling rake 0.9.2

gem uninstall rake
ERROR: While executing gem ... (Gem::InstallError)
cannot uninstall, check `gem list -d rake`

1) gem list -d rake

gives:

*** LOCAL GEMS ***

rake (0.9.2, 0.8.7)
Author: Jim Weirich
Rubyforge: http://rubyforge.org/projects/rake
Homepage: http://rake.rubyforge.org
Installed at (0.9.2): /Users/bparanj/.rvm/gems/ruby-1.9.2-p180@global
(0.8.7): /Users/bparanj/.rvm/gems/ruby-1.9.2-p180@global

2) rvm use @global && gem uninstall rake -v 0.9.2

uninstalls rake

Installing Ruby Debug

1) From the root of the project run:
gem install ruby-debug19 -- --with-ruby-include="$rvm_path/src/$(rvm tools identifier)/"

2) Include in Gemfile

group :test, :development do
gem ‘ruby-debug19′, :require => ‘ruby-debug’
end

3) Create a .rdebugrc in your home directory

set autolist
set autoeval
set autoreload
set forcestep


4)
Specify how you would like Rails to report deprecation notices for your bugger environment, set
config.active_support.deprecation to :log, :notify or :stderr at config/environments/bugger.rb


5) require 'ruby-debug' in development.rb. Edit source where you want to debug to include :

debugger

6) Start server in debug mode:
rails s -d

References

http://pivotallabs.com/users/chad/blog/articles/366-ruby-debug-in-30-seconds-we-don-t-need-no-stinkin-gui-
http://bashdb.sourceforge.net/ruby-debug.html
http://railscasts.com/episodes/54-debugging-with-ruby-debug

Uninstall all Gems in Ubuntu 10.04

gem list | cut -d" " -f1 | xargs sudo gem uninstall -aIx

Reference: Remove All Ruby Gems

Reserved Words You Can’t Use in Rails

It would be nice if the Rails generator fails to generate when you use the reserved words for a model. I wasted lot of time when I used words like monitor as a model name and class, type as an attribute for a model.

Here is a list of words that cannot be used.

List of types to use in script/generate model

he attributes are SQL types, hence the following are supported:

* :primary_key
* :string
* :text
* :integer
* :float
* :decimal
* :datetime
* :timestamp
* :time
* :date
* :binary
* :boolean

Stolen from stackoverflow

How to remove a ignore a file in git that is already in git?

git rm --cached

Reference: Git

Convert private to public repo in github

Go to edit and change the repo from private to public

Could not find nokogiri-1.4.4 in any of the sources on Ubuntu

If you get the error: "Could not find nokogiri-1.4.4 in any of the
sources" it is probably related to "libxm12" missing. In fact, that
library is probably there. What you are missing is the development
version:

sudo apt-get install libxml2-dev

nokogiri should then install.

Reference: Manual Install

Forcing DNS changes to take effect on Snow Leopard

I made a mistake while setting up the DNS on Linode. In order to flush the old DNS server settings. I had to run:

dscacheutil -flushcache

Then create a new zone with the right IP Address. Just ping the hostname to find the IP Address and check if it is correct by comparing it to the Linode dashboard.

How to highlight tabs in Rails

1) Include the following method in application helper.

def is_active?(page_name)
# logger.info("lllllllllllll #{page_name}")
# logger.info("cccccccccccccc #{params[:controller]}")
"current" if params[:controller] == page_name
end

2) In your layout, add this:

<%= link_to 'Articles', new_article_path, :class => is_active?("articles") %>


3) Uncomment the logger lines to see which controller is handling the request and just fill in
the parameters for is_active? method

Fixed an error from the code I found from an original post in Stackoverflow.

Installing Postgres on Snow Leopard

1) sudo port install postgresql83 postgresql83-server
2)

sudo mkdir -p /opt/local/var/db/postgresql83/defaultdb
sudo chown postgres:postgres /opt/local/var/db/postgresql83/defaultdb
sudo su postgres -c '/opt/local/lib/postgresql83/bin/initdb -D /opt/local/var/db/postgresql83/defaultdb'

3) sudo launchctl load -w /Library/LaunchDaemons/org.macports.postgresql83-server.plist

4) sudo su postgres -c '/opt/local/lib/postgresql83/bin/postgres -D /opt/local/var/db/postgresql83/defaultdb'

5) sudo vi /etc/profile

6) Add : PATH="/opt/local/bin:/opt/local/sbin:/opt/local/lib/postgresql83/bin:$PATH"

7) createuser --superuser your_macusername -U postgres

8) createdb my_database

9) sudo env ARCHFLAGS="-arch x86_64" gem install pg

10) database.yml
development:
adapter: postgresql
database: your_db
username: your_db_username

Installing pgAdmin

sudo port install pgAdmin3

Upon completion of installation, you can find the application in /Applications/MacPorts/pgAdmin3


Reference:
Installing PostgreSQL on Snow Leopard 10.6


Installing PostgreSQL on Leopard using MacPorts

No such file or directory - /tmp/mysql.sock

Fix : sudo ln -s /var/run/mysqld/mysqld.sock /tmp/mysql.sock

Reference : No such file or directory

How to customize Flash messages in Devise Rails gem

Customize the config/locales/devise.en.yml file in your project.

undefined local variable or method `confirmed_at' for

Devise Rails plugin throws this error when you don't have the

t.confirmable

in the users migration.

/etc/hosts file messed up on Snow Leopard

Whenever I run a Rails app, I had to access it via http://0.0.0:port_number. Devise Rails plugin sample app barks when redirecting with this error message:

ERROR URI::InvalidURIError: the scheme http does not accept registry part: 0.0.0:3000 (or bad hostname?)


1) To cleanup the mess, I edited the /etc/hosts file so it now looks like this:

##
# Host Database
#
# localhost is used to configure the loopback interface
# when the system is booting. Do not change this entry.
##
127.0.0.1 localhost
255.255.255.255 broadcasthost
::1 localhost
fe80::1%lo0 localhost

2) Then flush the cache to pickup the new changes by running :

sudo dscacheutil -flushcache

Now you can access your local Rails apps by : http://localhost:port_number and Devise is happy again.

sudo: no tty present and no askpass program specified

When trying to deploy to a new staging server, I get the following
error:

sudo: no tty present and no askpass program specified

Solution:

Add the line: default_run_options[:pty] = true
in your deploy.rb

Installing Sphinx on Snow Leopard

1. Download sphinx-0.9.9
2. ./configure
3. make
4. sudo make install

how to get all the branches that is remote in git

If you have many remote branches that you want to fetch at once:

$ git remote update
$ git pull --all

Now you can checkout any branch as you need to, without hitting the remote repo.


http://stackoverflow.com/questions/67699/how-do-i-clone-all-remote-branches-with-git

Source code formatter for Blogspot

Very useful source code formatter for blogspot

Ruby Programming Language Book Notes 2

| operator is used for union operation in Array.
& operator is used for intersection operation in Array.

1:  class Array  
2:       def union(another)  
3:        self | another  
4:       end  
5:       def intersection(another)  
6:        self & another  
7:       end  
8:  end  

Ruby Programming Language Book Notes

1)

minimum = if x < y then x else y end

can also be written as :

minimum = x < y ? x : y

2)

class Fixnum
def inclusive(element)
self..element
end

def exclusive(element)
self...element
end
end

This eliminates the mental mapping from .. and ... to the behaviour of the methods.

3) This does not work:

class Fixnum
alias inclusive ..
alias exclusive ...
end

gives syntax error, unexpected tDOT2

So how do you redefine the .. and ...? If you do ri Fixnum, it shows the instance methods. The section on Operators has discussion on operators that can be re-defined.

Convert Haml to ERB

1) script/plugin install http://github.com/cgoddard/haml2erb.git

2) In console:
hamls = Dir["app/views/**/*.haml"] - ['app/views/layouts/screen.html.haml'];
hamls.each do |haml|
puts haml
erb = haml.sub(/\.haml$/, '.erb')
File.open(erb, 'w') do |file|
file.write Haml2Erb.convert(File.read(haml))
end
end

http://makandra.com/notes/544-convert-haml-to-erb

ERROR: There has been an error fetching the ruby interpreter. Halting the installation.

This happens when there is no network connection. How wonderful it would be if developers can give error messages that make sense! Make the code robust and give users a clear call to action to rectify any errors that they can recover from. It is surprising that even ruby gems has the same issue.

Mispelled HTTP_REFERER in Rails 3.0

The correct spelling is HTTP_REFERRER but Rails source has it with wrong spelling. So in order to get the HTTP_REFERRER do the following in your controller:

request.env["HTTP_REFERER"]

request.domain has been deprecated. The domain method has been moved to ActionDispatch::Http::URL. Ideally we want to use the method defined in this module.Do to metaprogramming it is difficult to figure out the actual keys that are used in ActionDispatch::Request. If you run this snippet:

request.env.keys.each do |x|
logger.info x
end

You will get all the keys:

action_dispatch.request.formats
action_dispatch.request.parameters
rack.session
HTTP_ACCEPT
HTTP_HOST
SERVER_NAME
rack.request.cookie_hash
action_dispatch.remote_ip
rack.url_scheme
HTTP_KEEP_ALIVE
HTTP_USER_AGENT
REQUEST_PATH
action_dispatch.request.query_parameters
action_dispatch.request.unsigned_session_cookie
SERVER_PROTOCOL
HTTP_ACCEPT_LANGUAGE
rack.errors
action_dispatch.secret_token
async.callback
REMOTE_ADDR
PATH_INFO
rack.run_once
rack.version
SERVER_SOFTWARE
action_dispatch.request.path_parameters
rack.request.cookie_string
SCRIPT_NAME
HTTP_REFERER
action_dispatch.parameter_filter
HTTP_COOKIE
HTTP_VERSION
rack.multithread
action_dispatch.request.request_parameters
action_dispatch.cookies
REQUEST_URI
rack.multiprocess
rack.request.query_hash
SERVER_PORT
HTTP_ACCEPT_CHARSET
action_controller.instance
rack.session.options
async.close
REQUEST_METHOD
warden
rack.request.query_string
action_dispatch.request.content_type
GATEWAY_INTERFACE
HTTP_CONNECTION
HTTP_ACCEPT_ENCODING
QUERY_STRING
rack.input

Now you can access any of these environment values from your controller similar to the referrer.

Accessing Webrick running on VM from Mac OS

1) If the VM is running, stop it.

2) To forward from port 3001 on the host to port 3000 on the guest, run the following command on the host.
$ VBoxManage modifyvm "Ubuntu" --natpf1 "webrick,tcp,,3001,,3000"

3) To delete the port forwarding run:

VBoxManage modifyvm "Ubuntu" --natpf1 delete "webrick"

4) Now you can go to http://localhost:3001 on your host to hit webrick running on your VM.

The page loads very slow. Is there any way to speed it up?