Recent good notes

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 -%>

Require file from the same folder

If you want to require file from the same folder, the simplest way is

require File.expand_path('../file-to-require', __FILE__)

If your file is /lib/book.rb

File.expand_path('../page', '/lib/book.rb') => '/lib/page.rb'

Careful with this method.

Despite the name and description, it will actually update any changed fields on the model rather than just the desired attribute.

def update_attribute(name, value)
  send(name.to_s + '=', value)
  save(false)
end

See? Use update_all and pass in the model ID as a condition, instead.

Doesn't return nil on empty array when param is given

This does not return nil if the array is empty and n is given.

[].shift(2) # => []

a = []
a.shift(2) # => []
a # => []

Interpolating

Note that to interpolate, the sequences must be inside single quotes:

# replace /ll/ with itself
'hello'.gsub(/ll/, '\0') # returns 'hello'
'hello'.gsub(/ll/, "\0") # returns 'he\000o'

collect_with_index

Use Object#enum_for if you need to collect with index:

require 'enumerator'

['a', 'b', 'c'].enum_for(:each_with_index).collect do |item, index| 
  "#{index}: #{item}" 
end

See also: Enumerable#each_with_index

Can be used with has_many associations

You can also use this to validate that a has_many association has a specified number of records on the other end:

has_many :members

validates_length_of :members, :minimum => 1

Complete Formatting Codes

NOTE: Some of these seem only to work for DateTime (e.g. %L, %N)

%a - The abbreviated weekday name (“Sun”)

%A - The full weekday name (“Sunday”)

%b - The abbreviated month name (“Jan”)

%B - The full month name (“January”)

%c - The preferred local date and time representation

%C - Century (20 in 2009)

%d - Day of the month (01..31)

%D - Date (%m/%d/%y)

%e - Day of the month, blank-padded ( 1..31)

%F - Equivalent to %Y-%m-%d (the ISO 8601 date format)

%h - Equivalent to %b

%H - Hour of the day, 24-hour clock (00..23)

%I - Hour of the day, 12-hour clock (01..12)

%j - Day of the year (001..366)

%k - hour, 24-hour clock, blank-padded ( 0..23)

%l - hour, 12-hour clock, blank-padded ( 0..12)

%L - Millisecond of the second (000..999)

%m - Month of the year (01..12)

%M - Minute of the hour (00..59)

%n - Newline (n)

%N - Fractional seconds digits, default is 9 digits (nanosecond)

• %3N millisecond (3 digits)

• %6N microsecond (6 digits)

• %9N nanosecond (9 digits)

%p - Meridian indicator (“AM” or “PM”)

%P - Meridian indicator (“am” or “pm”)

%r - time, 12-hour (same as %I:%M:%S %p)

%R - time, 24-hour (%H:%M)

%s - Number of seconds since 1970-01-01 00:00:00 UTC.

%S - Second of the minute (00..60)

%t - Tab character (t)

%T - time, 24-hour (%H:%M:%S)

%u - Day of the week as a decimal, Monday being 1. (1..7)

%U - Week number of the current year, starting with the first Sunday as the first day of the first week (00..53)

%v - VMS date (%e-%b-%Y)

%V - Week number of year according to ISO 8601 (01..53)

%W - Week number of the current year, starting with the first Monday as the first day of the first week (00..53)

%w - Day of the week (Sunday is 0, 0..6)

%x - Preferred representation for the date alone, no time

%X - Preferred representation for the time alone, no date

%y - Year without a century (00..99)

%Y - Year with century

%z - Time zone as hour offset from UTC (e.g. +0900)

%Z - Time zone name

%% - Literal “%” character

t = Time.now                        #=> 2007-11-19 08:37:48 -0600
t.strftime("Printed on %m/%d/%Y")   #=> "Printed on 11/19/2007"
t.strftime("at %I:%M%p")            #=> "at 08:37AM"

Available statuses

All the available statuses (extracted from SYMBOL_TO_STATUS_CODE hash) in a slightly more readable form:

:continue                        => 100
:switching_protocols             => 101
:processing                      => 102
:ok                              => 200
:created                         => 201
:accepted                        => 202
:non_authoritative_information   => 203
:no_content                      => 204
:reset_content                   => 205
:partial_content                 => 206
:multi_status                    => 207
:im_used                         => 226
:multiple_choices                => 300
:moved_permanently               => 301
:found                           => 302
:see_other                       => 303
:not_modified                    => 304
:use_proxy                       => 305
:temporary_redirect              => 307
:bad_request                     => 400
:unauthorized                    => 401
:payment_required                => 402
:forbidden                       => 403
:not_found                       => 404
:method_not_allowed              => 405
:not_acceptable                  => 406
:proxy_authentication_required   => 407
:request_timeout                 => 408
:conflict                        => 409
:gone                            => 410
:length_required                 => 411
:precondition_failed             => 412
:request_entity_too_large        => 413
:request_uri_too_long            => 414
:unsupported_media_type          => 415
:requested_range_not_satisfiable => 416
:expectation_failed              => 417
:unprocessable_entity            => 422
:locked                          => 423
:failed_dependency               => 424
:upgrade_required                => 426
:internal_server_error           => 500
:not_implemented                 => 501
:bad_gateway                     => 502
:service_unavailable             => 503
:gateway_timeout                 => 504
:http_version_not_supported      => 505
:insufficient_storage            => 507
:not_extended                    => 510

stub_chain is very useful when testing controller code

or any other chained method call type that you’d like to stub, example:

in your controller:

def new
  @user = current_site.users.new
end

in your spec:

it "#new should assign a @user" do 
  u = mock("User")
  controller.stub_chain(:current_site, :users, :new).and_return(u)
  assigns[:user].should == u
end

whereas before you had to stub each chained method call separately:

it "#new should assign a @user" do 
  u = mock("User")
  users = mock("Users collection", :new => u)
  site = mock("Site", :users => users)
  controller.stub!(:current_site).and_return(site)
  assigns[:user].should == u
end

Please note that stub_chain was added to RSpec in version 1.2.6

Re: Caveat when using dynamic layouts

Since there’s no way to edit posts on here, I need to correct myself and say that what I posted before doesn’t work, since you can’t specify layout multiple times:

class OrdersController < BaseController
  layout :determine_layout, :only => :new
  layout "public", :except => :new
  # ...
end

So don’t do that. The only way to ensure that the other actions get the default theme is to drop :only/:except and do the conditions yourself:

class OrdersController < BaseController
  layout :determine_layout

private
  def determine_layout
    %w(new).include?(action_name) ? "some_layout" : "public"
  end
end

All this to say, beware of :only/:except – they aren’t as useful as you think they are.

Deprecated in 1.9.x!

Use FileUtils::copy instead. It is also in 1.8.x, FileUtils, so call that one instead.

makedirs(path) to create file path

mkdir will only create a single directory on an existing path. If you want to create a full path, like the `mkdir -p /full/path` command, use the makedirs method.

1.8: File.makedirs(path) 1.9: FileUtils.makedirs(path)

Caveat when using dynamic layouts

Worth noting that if you have a controller which inherits from another controller which has a layout, and in this child controller you’re determining the layout at runtime using a method for specific actions, the other actions you are excluding will not inherit the layout from the parent controller.

For example, if you’ve got this

class BaseController < ApplicationController
  layout "public"
end
class OrdersController < BaseController
  layout :determine_layout, :only => :new
  # index, show, new, create, edit, update, destroy ...
end

then OrdersController#index, #show, and #edit won’t get the “public” layout – in fact they won’t get a layout at all. So you’ll need to do this instead:

class OrdersController < BaseController
  layout :determine_layout, :only => :new
  layout "public", :except => :new
  # ...
end

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}
end

Article.new.published? # => true

However:

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

Article.new.published? # => false

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

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

Hash#except

Note that the ActiveSupport library provides the except and except! methods, which return the Hash minus the given keys. So you don’t need to write your own wrapper if you happen to be using Rails or ActiveSupport as a stand-alone library:

http://apidock.com/rails/ActiveSupport/CoreExtensions/Hash/Except/except

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:

Shirt.red.medium.alphabetical.current_scoped_methods
# ==>
{
  :create => {}, 
  :find => {
    :conditions => {:color => 'red', :size => 'medium'}, 
    :order => 'shirts.name ASC'
  } 
}

reload equivalent for models

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

Rmoving preceding 0's

In most *nix system, adding a - after the % will remove preceding 0s.

So %-d for a single digit day, or %-I for a single digit hour, etc.

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.

For the file path use File.dirname

File.dirname provides what File.basename omits.

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}") }

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'

Reverse version of camelize

Reverse version of camelize is underscore

Pretty way to test for current environment

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

Rails.env.development?
Rails.env.test?
Rails.env.production?
Rails.env.your_custom_environment?

Use this in controllers

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

include ActionView::Helpers::NumberHelper

Doesn't return nil if the object you try from isn't nil.

Note that this doesn’t prevent a NoMethodError if you attempt to call a method that doesn’t exist on a valid object.

a = Article.new

a.try(:author) #=> #<Author ...>

nil.try(:doesnt_exist) #=> nil

a.try(:doesnt_exist) #=> NoMethodError: undefined method `doesnt_exist' for #<Article:0x106c7d5d8>

This is on Ruby 1.8.7 patchlevel 174

Attribute names are Strings, not Symbols

Another possible gotcha – the returned hash keys are of type String, not Symbol:

user.attributes["login"] # => "joe"
user.attributes[:login] # => nil

Version Ranges

To specify a version range, use array syntax like this:

config.gem 'paperclip', :version => ['>= 2.3.1.1', '< 3.0']

The example will, of course, match any version 2.3.1.1 or newer up until (not including) 3.0 or later.