Notes posted to Ruby on Rails

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February 26, 2010
3 thanks

default_scope on create

If you specify :conditions in your default_scope in form of a Hash, they will also be applied as default values for newly created objects. Example:

class Article
  default_scope :conditions => {:published => true}

Article.new.published? # => true


class Article
  default_scope :conditions => 'published = 1'

Article.new.published? # => false
February 25, 2010
2 thanks

configuration no longer in environment.rb

configure session store in config/initializers/session_store.rb

February 25, 2010
1 thank

Saving other objects inside before_save

Don’t call .save or .update_attribute on other objects inside before_save callback.

Saving other objects inside of before_save callback results in flushing changed hash and the original object is not updated.

UPDATE observed sometimes, still investigating

February 25, 2010
1 thank


See ActiveRecord::ConnectionAdapters::TableDefinition#column for details of the options you can use.

February 25, 2010
2 thanks

Possible gotcha

This method returns a Pathname object which handles paths starting with a / as absolute (starting from the root of the filesystem). Compare:

>> Rails.root
=> #<Pathname:/some/path/to/project>
>> Rails.root + "file"
=> #<Pathname:/some/path/to/project/file>
>> Rails.root + "/file"
=> #<Pathname:/file>
>> Rails.root.join "file"
=> #<Pathname:/some/path/to/project/file>
>> Rails.root.join "/file"
=> #<Pathname:/file>
February 25, 2010
0 thanks

See documentation for the class method

Since Rails version 2, this instance method no longer exists.

You may be looking for its namesake class method, ActiveRecord::Base.method_missing

February 23, 2010
3 thanks

Easy workaround for missing :through option

Note that belongs_to does not support :through option like has_many (although IMHO it would make sense in some cases), but you can easily simulate it with delegate.

For example:

class Person < ActiveRecord::Base
  belongs_to :team
class Task < ActiveRecord::Base
  belongs_to :person
  delegate :team, :to => :person

There is of course more ways to do it, but this seems to be the easiest to me.

February 23, 2010
0 thanks

note: the example format regex is too lenient

The example regex for RFC 2822 email is too lenient. Sure it’s just an example, but it wound up in our code and we just had to fix it to match the RFC.

The regex as given allows any non-@ non-whitespace characters. But the RFC only allows these characters in mailbox names

alpha digit - ! \ # $ % & ' * + \ / = ? ^ _ ` { | } ~ ] +

and . is only allowed between atoms of 1 or more of the above.

Here’s the corrected regex:

:with => /\A([-a-z0-9!\#$%&'*+\/=?^_`{|}~]+\.)*[-a-z0-9!\#$%&'*+\/=?^_`{|}~]+@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i
February 16, 2010 - (>= v2.1.0)
3 thanks

Extract the aggregated scoping options

If you want to get the aggregated scoping options of a chain of named scopes use ActiveRecord::Base.current_scoped_methods

It works in the fashion of:

# ==>
  :create => {}, 
  :find => {
    :conditions => {:color => 'red', :size => 'medium'}, 
    :order => 'shirts.name ASC'
February 12, 2010
1 thank

re: Options

@ramanavel - The options are dependent on the cache store that you’re using. You’ll need to have a look at what the cache store you’re using allows.

e.g. MemCacheStore allows the use of time criteria based :expires_in, most of the cache stores don’t.

http://guides.rubyonrails.org/caching_with_rails.html might provide a little more information.

February 11, 2010
4 thanks

reload equivalent for models

The reset_column_information method provides a similar function for the model itself. Most useful during migrations.

February 9, 2010
0 thanks


What are all the options here please?…

February 5, 2010
2 thanks

the :order parameter is not sanitized

The :order parameter is not sanitized, so doing something like Person.find( :first , :order => params[:order] ) could get you in trouble.

February 5, 2010
2 thanks

An alternate way to have a string ID as a primary key

You can disable automatically created primary key and add it to manually with mysql:

The migration file:

def self.up

  create_table( :my_special_table, :id => false ) do |t|
    t.string :id, :limit => 5, :null => :no

  execute "ALTER TABLE my_special_table ADD PRIMARY KEY (id)"


Then in a before_save filter you can generate the primary key for yourself.

Use a transaction and be aware of uniqueness!

February 4, 2010 - (>= v2.1.0)
1 thank

All dates in the database are stored in UTC and all dates in Ruby are in a local timezone

With the timezone support introduced in Rails 2.1 the idea is that all dates in the database are stored in UTC and all dates in Ruby are in a local timezone.

Time.zone.now == Time.now # => false

as Peter Marklund lights up this in his blog:


“They will only be converted to UTC for you if they are ActiveSupport::TimeWithZone objects, not if they are Time objects. This means that you are fine if you use Time.zone.now, 1.days.ago, or Time.parse(”2008-12-23“).utc, but not if you use Time.now or Time.parse(”2008-12-23“)”

January 30, 2010
3 thanks

Paying attention to query parameters

Standard action caching ignores query parameters, which means you’d get the same results for a URL with and without query parameters if it was action cached. You can make it pay attention to them by using a custom cache path like so:

caches_action :my_action, :cache_path => Proc.new { |c| c.params }

Or, maybe you want some of the query parameters, but not all to factor into different versions of that action’s cache:

:cache_path => Proc.new { |c| c.params.delete_if { |k,v| k.starts_with?('utm_') } }

Beware of things like pagination if you use expires_in to expire the cache, as pages could get out of sync.

January 29, 2010
1 thank

Passing html options (Ruby hash parameters)

When you have two default hash parameters at the end of a function call, you need to use it as the following:

options = { :include_blank => true, :default => @my_object.my_method }

date_select :my_object, :my_method, options, :class => 'my_css_class'

You can try it for yourself on this example:

def test_funct a = {}, b = {}
  puts "a: #{a.inspect}"
  puts "b: #{b.inspect}"

test_funct :x => 'x', :y => 'y'  # all the parameters are collected for the hash a
January 27, 2010
1 thank

Alternative hostname generation method

Instead of using a random number to generate the hostname for the single asset, I prefer using source.hash.modulo, so that a given file is always served from the same host. This makes the content more cacheable by browsers and proxies.

ActionController::Base.asset_host = Proc.new { |source|
  "http://assets#{ source.hash.modulo(9) }.example.com"

I didn’t benchmark how long it takes, but String#hash should be reasonably fast.

January 26, 2010 - (>= v2.3.2)
1 thank

is now a subclass of Hash that preserves order (or _is_ a Hash if running Ruby 1.9 or greater)

You might not realize it preserves order because it delegates inspect to its super-class, Hash, which doesn’t preserve order. But you will see that order is preserved if you iterate or use the keys or values methods:

>> names = ['Amy Irving', 'Jane Doe', 'John Doe', 'John Updike', 'Susan Anthony']
>> ordered = names.group_by { |name| name.split.first }
=> #<OrderedHash {"John"=>["John Doe", "John Updike"], "Amy"=>["Amy Irving"], "Susan"=>["Susan Anthony"], "Jane"=>["Jane Doe"]}>

>> ordered.keys
=> ["Amy", "Jane", "John", "Susan"]

>> ordered.each { |first, full| puts first; full.each { |name| puts "  "+name } }
  Amy Irving
  Jane Doe
  John Doe
  John Updike
  Susan Anthony
January 26, 2010 - (>= v2.3.2)
2 thanks

returns an ActiveSupport::OrderedHash

Returns an ActiveSupport::OrderedHash, which is a subclass of Hash that preserves order. If you’re running Ruby 1.9, it is simply an alias for Hash. Surprisingly, you might not realize that OrderedHash is preserving order since it delegates its inspect method to Hash. More at ActiveSupport::OrderedHash.

January 21, 2010
3 thanks

W3CDTF Format

Here is the formatted string for the W3CDTF datetime format (http://www.w3.org/TR/NOTE-datetime). It has a semicolon in the timezone part, therefore you cannot use ‘%z’:

Time::DATE_FORMATS[:w3cdtf] = lambda { |time| time.strftime("%Y-%m-%dT%H:%M:%S#{time.formatted_offset}") }
January 20, 2010
4 thanks

Using html text instead of default response

If you have a string containing html and want to assert_select against it, as the doc states you have to pass in an element (HTML::Node) as the first argument. You can do something like this:

doc = HTML::Document.new('<p><span>example</span></p>')
assert_select doc.root, 'span'
January 20, 2010
2 thanks

Escape brackets in selector

If you need to escape brackets in a selector, this is the way to do it:

assert_select "input[type=hidden][name='user[role_ids][]']"
January 20, 2010
3 thanks
January 18, 2010
1 thank

Undeprecated version

The undeprecated version of this function is here: ActionView::Helpers::PrototypeHelper#link_to_remote

January 16, 2010 - (>= v2.2.1)
8 thanks

Pretty way to test for current environment

You can check your current Rails environment using nice methods such as:

January 15, 2010
3 thanks

Use this in controllers

Sometimes you’re gonna need this in controllers. Just put this in the controller:

include ActionView::Helpers::NumberHelper
January 14, 2010
0 thanks

:find takes more keys than written

The documentation says that the :find keywords “may include the :conditions, :joins, :include, :offset, :limit, and :readonly options”. Note that this does not mean that only those options are supported. :sort also works like it should, for example.