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January 9, 2009
3 thanks

Adding params to generated url

Whenever you want to append custom parameters to a to be generated url it might be necessary to stop url_for from escaping.

url_for(:action => 'some_action', :custom1 => 'some_value', :custom2 => 'some_value', :escape => false)

If the escape => false option is not passed the generated url contains & instead of the correct &-sign.

January 8, 2009
10 thanks

Refactoring excessive code for selects

@garg: It is not recommended to have excessive code in the views. You should refactor your code a bit.

<%= f.select(:manufacturer_id, Manufacturer.find(:all).collect {|u| [u.name, u.id]}, :prompt => 'Select') %>

could be changed to this:

# in app/helpers/manufacturer_helper.rb
def manufacturers_for_select
  Manufacturer.all.collect { |m| [m.name, m.id] }

# in the view
<%= f.select(:manufacturer_id, manufacturers_for_select, :prompt => 'Select') %>

I would look into collection_select though:

<%= f.collection_select(:manufacturer_id, Manufacturer.all, :id, :name, :prompt => 'Select') %>

It’s much more clean and you don’t have to define a helper for it to be readable (altough it’s still quite long).

If you have to do this often, you should define a FormBuilder extension, so you get methods like f.manufacturer_select:

<%= f.manufacturer_select(:manufacturer_id, Manufacturer.all) %>

IMO, most projects should have a custom form builder anyway, so the addition would be very small. This is my personal opinion, so you don’t have to listen to it. :-)

January 8, 2009
5 thanks

Watch out for syntax errors

Watch out when you are using returning with hashes. If you would write code like

def foo(bars)
  returning {} do |map|
    bars.each { |bar| map[bar.first] = bar }

you will get a syntax error since it looks like you tried to supply two blocks! Instead you should write it with parenthesis around the hash:

def foo(bars)
  returning({}) do |map|
    bars.each { |bar| map[bar.first] = bar }
January 6, 2009
5 thanks

Default allowed tags and attributes

I found it a bit hard to find the default tags and attributes in the docs.

As of Rails 2.2.2 they are:


del, dd, h3, address, big, sub, tt, a, ul, h4, cite, dfn, h5, small, kbd, code,
b, ins, img, h6, sup, pre, strong, blockquote, acronym, dt, br, p, div, samp,
li, ol, var, em, h1, i, abbr, h2, span, hr


name, href, cite, class, title, src, xml:lang, height, datetime, alt, abbr, width

Getting the latest list

You can query for this list yourself with the following code on the console:

>> puts helper.sanitized_allowed_tags.to_a * ", "
... will output tag list ...
>> puts helper.sanitized_allowed_attributes.to_a * ", "
... will output attribute list ...

The same principal can probably be applied to sanitize_css.

January 2, 2009 - (v2.0.0 - v2.2.1)
3 thanks

What to use instead

For versions 2.0+, use ActiveRecord::Base::sanitize_sql_array

January 2, 2009
3 thanks

current_action? and current_controller?

I use them in link_unless_current_controller helper.

def current_action?(options)
  url_string = CGI.escapeHTML(url_for(options))
  params = ActionController::Routing::Routes.recognize_path(url_string, :method => :get)
  params[:controller] == @controller.controller_name && params[:action] == @controller.action_name

def current_controller?(options)
  url_string = CGI.escapeHTML(url_for(options))
  params = ActionController::Routing::Routes.recognize_path(url_string, :method => :get)
  params[:controller] == @controller.controller_name
December 24, 2008 - (>= v2.2.1)
5 thanks

uninitialized constant ActionView::Base::CompiledTemplates::TimeZone

If you get this error, you need to use ActiveSupport::TimeZone.us_zones instead of TimeZone.us_zones.


<%= form.time_zone_select(:time_zone, ActiveSupport::TimeZone.us_zones) %>
December 16, 2008 - (v1.0.0 - v2.2.1)
11 thanks

Force initial value

If you want to force an initial value for your text_field which is normally based on your object attribute value, you can use :

text_field :ecard, :sender, :value => 'contact@host.com'
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 6, 2008
5 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 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


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 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 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 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
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
3 thanks

Add spacer template

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

November 6, 2008
4 thanks


exact url from browser window:

def current_url
  url_for :only_path=>false,:overwrite_params=>{}
October 30, 2008
7 thanks

Can be extended but only with a module

Although not documented, belongs_to does support Association Extensions however it doesn’t accept a block like has_many does. So you can’t do this:

class Account < ActiveRecord::Base
  belongs_to :person do
    def do_something_funky
      # Some exciting code

but you can do this:

module FunkyExtension
  def do_something_funky
    # Some exciting code

class Account < ActiveRecord::Base
  belongs_to :person, :extend => FunkyExtension

And then call it like this:

@account = Account.first
October 29, 2008
3 thanks

A work-around for adding confirmation to image_submit_tag

Sometimes you may want to add a confirmation to image submit tags but this function does not allow it. To get over this limitation use a normal submit tag and set the src and type properties (set type to “image”)

Code example

submit_tag “Delete”, :confirm => “Are you sure?”, :src => “/images/trash.png”, :type => “image” %>