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December 12, 2008
7 thanks

acts_as_state_machine named scopes

If you are using the acts_as_state_machine plugin, this will generate all named scopes for your various states.

Place it after the acts_as_state_machine and state declarations.

class Task < ActiveRecord::Base
  acts_as_state_machine :initial => :waiting
  state :waiting
  state :running
  state :finished    

  states.each { |s| named_scope s, :conditions => { :state => s.to_s } }

Then doing a Task.waiting will return the corresponding tasks.

December 11, 2008
3 thanks

with resources



# => true
December 11, 2008 - (>= v1.0.0)
5 thanks

Calling migrations within migrations

It’s very occasionally a wise strategy to call migrations from within other migrations. This is typically done when you are adding a migration that deletes a now-obsolete table.

Let’s say one night when you were drunk or otherwise not thinking straight you did something like this:

class CreateExGirlfriendTexts < ActiveRecord::Migration
  def self(dot)up
    create_table :ex_girlfriend_texts { |t| ... }

  def self(dot)down
    drop_table :ex_girlfriend_texts

Oops! You could add this for your “undo” migration the next morning:

class FixDrunkMistake < ActiveRecord::Migration
  def self(dot)up

  def self(dot)down

Now, in the event you decide you really did like that table, you can always get it back easily. Keep in mind this will be made more complicated if your table is modified over multiple transactions.

December 11, 2008
6 thanks

Accessing aggregate methods with :group

You can access aggregate methods (such as SUM, COUNT, etc.) when using a JOIN and GROUP BY query by simply naming the aggregate columns and calling them as methods on the returned objects:

hits_by_page = WebpageHit.all({
  :select => "webpages.*, COUNT(webpage_hit.id) AS view_count",
  :joins => :webpage,
  :group => "webpages.id"
homepage_hits = hits_by_page[homepage.id].view_count

The view_count method is added to the Webpage model by this call. Note, however, that this method returns a string, and is not typecasted by Rails.

December 10, 2008
0 thanks



December 6, 2008
4 thanks

Array expansion in blocks

The syntax can be improved as changing the second parameter of the block (values) and using an array of two variables instead, which will be used by Ruby as the key and value of “array”.

array = [['A', 'a'], ['B', 'b'], ['C', 'c']]

hash = array.inject({}) do |memo, (key, value)|
  memo[key] = value

# => {'A' => 'a', 'B' => 'b', 'C' => 'c'}
December 6, 2008
0 thanks

:cache_path strangeness

I’ve noticed that using an example like this one shown in the docs has some issues with URI escaping:

caches_action :feed, :cache_path => Proc.new { |controller|
     controller.params[:user_id] ?
       controller.send(:user_list_url, controller.params[:user_id], controller.params[:id]) :
       controller.send(:list_url, controller.params[:id]) }

When I do this, the :myroute_url methods return URLs with escaped parameters, as one would expect, but for some reason Rails unescapes these strings by the time it uses them to store the cache blob. This is messing up my cache expiration routines, because they keep track of the escaped versions of the urls that are returned by the routing methods, not the unescaped versions. It would be easier if Rails didn’t do any magic to the string and simply used exactly what you pass to cache_path.

December 3, 2008 - (v2.2.1)
5 thanks

Method doesn't exists

Don’t confuse it with new_record? in ActiveRecord

December 2, 2008
5 thanks

From the official docs

enum.inject(initial) {| memo, obj | block } => obj enum.inject {| memo, obj | block } => obj

Combines the elements of enum by applying the block to an accumulator value (memo) and each element in turn. At each step, memo is set to the value returned by the block. The first form lets you supply an initial value for memo. The second form uses the first element of the collection as a the initial value (and skips that element while iterating).

# Sum some numbers
(5..10).inject {|sum, n| sum + n }              #=> 45
# Multiply some numbers
(5..10).inject(1) {|product, n| product * n }   #=> 151200

# find the longest word
longest = %w{ cat sheep bear }.inject do |memo,word|
   memo.length > word.length ? memo : word
longest                                         #=> "sheep"

# find the length of the longest word
longest = %w{ cat sheep bear }.inject(0) do |memo,word|
   memo >= word.length ? memo : word.length
longest                                         #=> 5


December 1, 2008 - (>= v2.2.1)
1 thank

Upgrading from Rails v2.1 to v2.2

Don’t forget to run

rake gems:refresh_specs

if you vendored any gem plugins under Rails v2.1 to update them with the proper specs.

November 28, 2008 - (>= v2.2.1)
2 thanks

Removed form Rails core

country_select and country_options_for_select were removed from Rails core since 2.2 release, but extracted to plugin. http://github.com/rails/country_select/tree/master/README

Also you could be interested in localized_country_select plugin which uses Rails internationalization framework I18n. http://github.com/karmi/localized_country_select/tree/master/README.rdoc

November 26, 2008
10 thanks

Types array shorthand

You can have respond_to blocks that look like this:

respond_to do |format|

Here each individual format doesn’t receive a block and so Rails automatically tries to render the appropriate view for the mime type (e.g. action.html.erb, action.xml.erb or as a last resort action.erb)

You can do exactly the same thing by passing an array of Mime types to respond_to like this:

respond_to(:html, :xml)
November 24, 2008 - (<= v2.2.1)
7 thanks

Full List of Supported Formats

With a sample date of December 25th, 2008, at 14:35:05:

:db           # => 2008-12-25 14:35:05
:number       # => 20081225143505
:time         # => 14:35
:short        # => 25 Dec 14:35
:long         # => December 25, 2008 14:35
:long_ordinal # => December 25th, 2008 14:35
:rfc822       # => Thu, 25 Dec 2008 14:35:05 +0000
November 21, 2008 - (>= v2.0.0)
0 thanks


Install the plugin by typing

script/plugin install auto_complete

Remember to restart webservice :)

November 20, 2008
1 thank
November 20, 2008 - (<= v2.1.0)
0 thanks

Problematic :scroll option

If you use the :scroll => true option, note that at http://github.com/madrobby/scriptaculous/wikis/sortable-create it says:

“If you want your sortable list to be scrollable, wrap the list in a div and set the div to scrollable as apposed to making the ul element scrollable. Also, in IE you must set “position:relative” on the scrollable div.”

November 19, 2008
9 thanks

Formatting options

Readable strftime

%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

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

%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)

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

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

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

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

%U - Week number of the current year, starting with the first Sunday as the first day of the first week (00..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 name %% - Literal “%’’ character t = Time.now t.strftime(“Printed on %m/%d/%Y”) #=> “Printed on 04/09/2003” t.strftime(“at %I:%M%p”) #=> “at 08:56AM”

November 18, 2008
8 thanks

Pop for last, Shift for first

If you want to pop the first element instead of the last one, use shift .

November 16, 2008 - (>= v2.1.0)
11 thanks

Application Helper for Fading Flash Messages

A simple helper method for showing the flash message. Includes optional fade in seconds (view needs javascript_include_tag defaults if you desire fade effect):

def show_flash_message(options={})
  html = content_tag(:div, flash.collect{ |key,msg| content_tag(:div, msg, :class => key) }, :id => 'flash-message')
  if options.key?(:fade)
    html << content_tag(:script, "setTimeout(\"new Effect.Fade('flash-message');\",#{options[:fade]*1000})", :type => 'text/javascript')

simply call in your views then using:

<%= show_flash_message(:fade => 4) %>
November 16, 2008
1 thank

:select multiple fields

it might be obvious or not:

Task.find :all, :select => "name, members"
November 14, 2008
0 thanks
November 12, 2008
6 thanks

Another Example

Do not mistakenly pass class_name as a key/value pair (Hash form). You will get an error including the text ‘class or module needed’. It should look like this:

serialize :some_array, Array

Or, perhaps clearer would be:

serialize(:some_array, Array)

That may seem obvious, but it is common to be in the habit of passing things as a key/value pair.

November 12, 2008
1 thank

Ajax form

<% form_remote_tag :url => { :action => “analyze”}, :update => “result” do %>

  <%= select_tag 'company_id', options_for_select([]) %><br/>
  <%= text_area_tag :text, nil, { :cols => 100, :rows => 10 }%><br/>
  <%= submit_tag "Analyze", :disable_with => "Please wait..." %>
<% end %>
<div id="result"></div>
November 11, 2008
4 thanks

:use_route to force named routes in url_for

If you are using a plugin or library that calls url_for internally, you can force it to use a particular named route with the :use_route key. For instance, calling:

url_for(:controller => 'posts', :action => 'view', :id => post, :use_route => :special_post)

will have the same effect as:


Naturally, this is much more verbose if you’re calling it directly, but can be a lifesaver if url_for is being called inside another method (e.g. will_paginate).

November 7, 2008
3 thanks

Re: Using a Loading Graphic

You probably want to be using :complete, not :loaded, to execute Javascript when an Ajax request has finished. See: http://prototypejs.org/api/ajax/options

November 7, 2008 - (v1.0.0 - v2.1.0)
0 thanks

Using your model's connection

It’s possible to execute raw SQL over the currently established connection for a model.

You may configure Rails to use different databases for different models. To make sure you are querying the correct database you may do the following:

MyModel.connection.execute("UPDATE `my_models` SET `beer`='free' WHERE 1")
November 7, 2008
3 thanks

Common options

“Common options” mentioned here is default PrototypeHelper options documented in link_to_remote

This means you can use :loading, :loaded, :failure, :success, etc in observe_field.

November 7, 2008
2 thanks

Parsing YAML from a POST request

When building a REST server which should accept YAML there are several things to take into consideration.

First of the client should tell the server what type of data it is going to send. This is done via the Content-Type header (which is NOT only a response header as opposed to what the RESTful Web Services book from O’Reilly made us believe).

Second the server application should know how handle the body of the POST request. Placing the following line in your environment.rb:

ActionController::Base.param_parsers[Mime::YAML] = :yaml

This registers the YAML parser. Smooth sailing from here on!

November 7, 2008
3 thanks

Add spacer template

<%= render :partial => “product”, :collection => @products, :spacer_template => “product_ruler” %>

November 6, 2008 - (v1_8_6_287)
1 thank

Missing Documentation

Returns false if obj <=> min is less than zero or if anObject <=> max is greater than zero, true otherwise.

3.between?(1, 5)               #=> true
6.between?(1, 5)               #=> false
'cat'.between?('ant', 'dog')   #=> true
'gnu'.between?('ant', 'dog')   #=> false