Notes posted to Ruby on Rails

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July 16, 2010
4 thanks

to set NULL => NO

use :null => false

change_column :my_table, :my_column, :integer, :default => 0, :null => false
July 16, 2010
2 thanks

Changing to MySql:BIGINT

I can change a column type from INT to BIGINT with this command:

change_column :my_table, :my_column, :bigint
July 15, 2010 - (<= v2.3.8)
2 thanks
July 15, 2010
0 thanks

Doesn't output into STDOUT

Oddly enough it runs a rake task without any sort of output. To get around it you can simple substitute it with:

puts run('rake your_task')

Unless somebody has a better idea?

July 14, 2010
2 thanks
July 14, 2010
0 thanks

If you need to pass a value

In the above example ‘value’ happens to be either true or false depending if the option was passed in or not. If you wish to capture an actual value you’ll want something like this:

def add_options!(opt)
  opt.on('-option=value') { |value| options[:option] = value }
July 14, 2010
6 thanks


You can scope uniqueness as well

validates :user_name, :presence => true, :uniqueness => {:scope => :account_id}

# the old way  
validates_uniqueness_of :user_name, :scope => :account_id
July 14, 2010
1 thank
July 10, 2010
2 thanks



That has nothing to do with IE. When you specify :cache => true you are saying that the files referenced should be saved to a file called all.js. When the script encounters the next line, it will overwrite the same file with the new contents.

Caching is not compressing, it doesn’t make sense to do with individual files, but it can make sense some times. I someone wants to do it, just specify a name for the cached file:

javascript_include_tag 'layout', 'typography', :cache => 'base'
javascript_include_tag 'admin/layout', 'admin/extras', :cache => 'admin'
July 9, 2010 - (>= v2.2.1)
0 thanks

Separator default is not always "." but depends on locale

Locale en:

number_with_precision(111.2345)  # => 111.235

Locale fr-FR:

number_with_precision(111.2345)  # => 111,235

Same with delimiter.

July 8, 2010
1 thank

Destroying Data

As far as I can tell, at least on a migration of a column from an integer to a decimal, this does not get rid of existing data.

July 8, 2010 - (>= v2.1.0)
1 thank

Rails v2.1.0 has built-in time-zone support

Rails versions as of 2.1.0 have basic timezone support built-in to the Time object. However, to get a list of all the timezones you need to install the tzinfo gem.


All contries, all timezones:

TZInfo::Country.all.sort_by { |c| c.name }.each do |c|
  puts c.name # E.g. Norway
  c.zones.each do |z|
    puts "\t#{z.friendly_identifier(true)} (#{z.identifier})" # E.g. Oslo (Europe/Oslo)

TZInfo::TimeZone.get(identifier) returns a TimeZone -object by the identifier.

July 4, 2010
2 thanks

Common use

I typically use require_dependency when developing a class or module that resides in my rails app, perhaps in the lib/ dir. A normal require statement does not reload my changes, so I use require_dependency in files that reference my newly developed class or module.

July 2, 2010
0 thanks

Takes array

Like assert_difference this method can take an array of expressions to evaluate all of them. For example:

assert_no_difference ['Publisher.count', 'User.count', 'Membership.count'] do
  post :create

It creates an assertion for each item in the array. So this will add three assertions to your test.

June 24, 2010
0 thanks


<div style=“margin:0;padding:0”>

<input name="authenticity_token" type="hidden" value="f755bb0ed134b76c432144748a6d4b7a7ddf2b71" /> 


Helper generates a div element with a hidden input inside. This is a security feature of Rails called cross-site request forgery protection and form helpers generate it for every form whose action is not “get”.

June 23, 2010
0 thanks

Getting the client ip

From CgiRequest you can get the client ip in controller:

June 23, 2010
2 thanks

Accessing controller data

You can access controller attributes from views via the @controller variable.

It has some important attributes:

  • @controller.controller_name -> the name of the controller

  • @controller.request -> returns the ActionController::Request

    • @controller.request.method -> the request method ( get, post, put, delete )

    • @controller.request.host -> the request host ( ip address or hostname ) where your server runs

    • @controller.request.ip -> the ip where your browser runs

June 23, 2010
1 thank

how I use it

def rescue_action_in_public(exception)

case exception

when ActiveRecord::RecordNotFound, ActionController::UnknownAction, ActionController::RoutingError
  redirect_to errors_path(404), :status=>301
  redirect_to errors_path(500)


June 18, 2010
8 thanks

multiple attributes with the same validations

You can list multiple attributes if they share the same validations

validates :title, :body, :presence => true

sending the attributes as an array will return an error

validates [:title, :body], :presence => true
#=> ArgumentError: Attribute names must be symbols
June 18, 2010
0 thanks

Careful when updating foreign key directly

Seems when you change key directly it doesn’t update association automatically.

>> chicken = Chicken.first
>> chicken.head
=> old_head
>> chicken.head_id = new_head.id
>> chicken.head
=> old_head

Easy (stupid?) way to fix it:

class Chicken
  def head_id=(value)
    self.head = Head.find_by_id(value)
June 13, 2010 - (>= v2.3.8)
0 thanks

Positioning the column. MySQL only

Add support for MySQL column positioning via #add_column and #change_column

add_column and change_column in the MySQL adapter now accept some additional options:

:first => true # Put the column in front of all the columns

:after => column_name # Put the column after ‘column_name’

class AddLastNameToUsers < ActiveRecord::Migration
  def self.up
    add_column :users, :last_name, :after => :first_name

  def self.down
    remove_column :users, :last_name


class AddIdToUsers < ActiveRecord::Migration
  def self.up
    add_column :urers, :id, :first => true

  def self.down
    remove_column :users, :id
June 7, 2010
2 thanks

No security

One important thing to remember is that this is NOT hidden in the source code and can be modified by an evil user so all input in a hidden field should be considered as untrustworthy and checked just like a visible field.

June 4, 2010
2 thanks

database exceptions will still be raised

Note that save() only returns false on validation errors (when valid? returns false). If other errors occur at the database level, like a database deadlock or trying to insert null into a column that doesn’t allow it, that will still raise an exception.

May 31, 2010
4 thanks

Naming fragment cache

One of the common ways of using fragment caching is to cache content that’s shared across the site (eg. left navigation, menus, widgets etc.) that looks and works the same regardless of the name of the action or controller calling it. In such cases it’s very easy to just use named fragment caching eg.:

<% cache('left_nav') do -%>
  <%= display_left_nav -%>
<% end -%>
May 27, 2010
2 thanks

Use :path_prefix for the namespace

Resources are added after the :path_prefix. However if you use a :path_prefix on a resource, it overrides the namespace path instead of appending to it (as I think it should).

Here is what I wrote to create a versioned API access path.

map.namespace :api3, :path_prefix=>"/api/v3" do |api|
  api.resources :posts
  api.resources :comments, :path_prefix=>"/api/v3/post/:post_id"

This will create routes like

path: /api/v3/posts/1 
named_route: api3_post()
May 26, 2010
0 thanks

Prevent transactional fixtures for a specific test class

If you want to prevent a specific group of tests from being run inside a transaction, just define inside your test class the methods teardown_fixtures and setup_fixtures with empty bodies.

May 26, 2010
0 thanks

Prevent transactional fixtures for a specific suite

If you want to prevent a specific group of tests from being run inside a transaction, just define inside your test class the methods teardown_fixtures and setup_fixtures with empty bodies.

May 18, 2010
2 thanks

How using Array methods

It’s not possible to use Array methods with a scope because it’s not an Array but an ActiveRecord::NamedScope::Scope :



doesn’t run.

But you can use the to_a method to transform the ActiveRecord::NamedScope::Scope to an Array :

May 14, 2010
0 thanks

You must use the yielded object

A warning note (at least for v2.3.4): if you don’t use the yielded format object, you will get a cryptic error like this:

NoMethodError (You have a nil object when you didn't expect it!
The error occurred while evaluating nil.call):
 app/controllers/comments_controller.rb:11:in `create'

So make sure you use it!

May 11, 2010
1 thank

No Layout, other options

While it renders to the same rules as render, you need to specify params.

You’d think this would work:

render_to_string "users/profile", :layout => false

You need to do this instead

render_to_string(:layout => "users/profile", :layout => false)