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:

Tags

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

Attributes

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.

What to use instead

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

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
end

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
end

link_to_if for named routes

Back before named routes we used to say things like:

<%= link_to_if message.user, 'Poster', :controller => 'users',
  :action => 'show', :id => message.user %>

This would make the text “Poster” only link if message has a user. But with named routes this has become more complicated. Our first try is something like:

<%= link_to_if message.user, 'Poster', user_path(message.user) %>

Although this looks nice it causes an error since the path is generated prior to the condition not after the condition like using a hash is done. To get around this problem I have found two solutions:

• If you are linking to the “show” path then you can just pass the object. This will force the path to not be generated until after the condition (like a hash is done). For example:

  <%= link_to_if message.user, 'Poster', message.user %>
  

• The previous workaround works great if you want to link to the show action. But what if you want to link to another action (say the edit action). In this case the best way I have found is to use the hash_for* helpers generated with the routing resource. So:

  <%= link_to message.user, 'Poster',
    hash_for_edit_user_path(:id => message.user) %>
  

A little more awkward than the previous workaround but it is the best I can come up with. Any other suggestions (other than going back to manually typing the hash)?

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

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

Example:

<%= form.time_zone_select(:time_zone, ActiveSupport::TimeZone.us_zones) %>

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'

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 } }
end

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

with resources

/products

current_page?(products_path)

# => true

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| ... }
  end

  def self(dot)down
    drop_table :ex_girlfriend_texts
  end
end

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

class FixDrunkMistake < ActiveRecord::Migration
  def self(dot)up
    CreateExGirlfriendTexts.down
  end

  def self(dot)down
    CreateExGirlfriendTexts.up
  end
end

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.

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.

Method doesn't exists

Don’t confuse it with new_record? in ActiveRecord

Types array shorthand

You can have respond_to blocks that look like this:

respond_to do |format|
  format.html
  format.xml
end

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)

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

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')
  end
  html
end

simply call in your views then using:

<%= show_flash_message(:fade => 4) %>

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.

: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:

special_post_url(post)

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).

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

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.

Add spacer template

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

current_url

exact url from browser window:

def current_url
  url_for :only_path=>false,:overwrite_params=>{}
end

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
    end
  end
end

but you can do this:

module FunkyExtension
  def do_something_funky
    # Some exciting code
  end
end

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

And then call it like this:

@account = Account.first
@account.person.do_something_funky

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” %>

Also for numeric

1.humanize == “1″ 1000000.humanize == “1.000.000″ 1000.12345.humanize == “1.000,12″

http://pragmatig.wordpress.com/2008/10/25/numbers-for-humans-humanize-for-numeric/

Prompt vs. Select

According to the docs in form_options_helper.rb

:include_blank - set to true or a prompt string if the first option element of the select element is a blank. Useful if there is not a default value required for the select element.

:prompt - set to true or a prompt string. When the select element doesn’t have a value yet, this prepends an option with a generic prompt – “Please select” – or the given prompt string.

The main difference is that if the select already has a value, then :prompt will not show whereas the :include_blank always will.

Back it up with a unique index

As mentioned briefly above, as well as using this validation in your model you should ensure the underlying database table also has a unique index to avoid a race condition.

For example:

class User < ActiveRecord::Base
  validates_uniqueness_of :login_name
end

The index can be specified in the migration for the User model using add_index like this:

add_index :users, :login_name, :unique => true

You do a similar thing when using the :scope option:

class Person < ActiveRecord::Base
  validates_uniqueness_of :user_name, :scope => :account_id
end

Should have a migration like this:

add_index :people, [ :account_id, :user_name ], :unique => true

Note that both the attribute being validated (:user_name) and the attribute(s) used in the :scope (:account_id) must be part of the index.

For a clear and concise explanation of the potential for a race condition see Hongli Lai’s blog.

Customizing attribute names in error messages

By default, the error messages translate the names of the attributes through String#humanize. The way to to change that is to override the ActiveRecord::Base.human_attribute_name method.

For example, if you want to name a column in your database as :www_url and you want to say “Website” instead of “Www url” in the error message, you can put this into your model:

class Person < ActiveRecord::Base
  def self.human_attribute_name(attribute_key_name)
    if attribute_key_name.to_sym == :www_url
      "Website"
    else
      super
    end
  end
end

Currently this seems to be the cleanest and easiest way. Unfortunately, human_attribute_name is deprecated and may stop working in a future release of Rails.

Gotcha when defining :finder_sql or :counter_sql

When setting custom SQL statements in the :finder_sql or :counter_sql queries, if you need to inject attributes from the current object, such as the ID, make sure to disable string interpolation of the statement by using single quotes or %q().

Example:

has_many :relationships, :class_name => 'Relationship', :finder_sql => %q(
  SELECT DISTINCT relationships.*
  FROM relationships
  WHERE contact_id = #{id}
)

Surrounding this SQL with double-quotes or %Q() will expand #{id} too early, resulting in a warning about Object#id being deprecated and general brokenness.

Using a Loading Graphic

If you want to make a little loading graphic, typically you use an animated gif (like a little spinner or something). Both link_to_remote and remote_form_for allow you to easily do this by using the :loaded and :loading triggers to call javascript.

For example:

<% remote_form_for @survey, :loading => "$('loading').show();", :loaded => "$('loading').hide();" do |f| %>
  <%= submit_tag ' Save' %>
  <%= image_tag "indicator_circle.gif", :style => 'display: none;', :id => 'loading' %>
<% end %>

The ‘loading’ parameter used for the ‘$’ prototype selector is the id of the animated gif. It starts out hidden, and is toggled by the loading/loaded triggers.

Opening a link in a new window

Use “_blank”, not “_new” to open a link in a new window.

link_to "External link", "http://foo.bar", :target => "_blank"
# => <a href="http://foo.bar" target="_blank">External link</a>

number_to_euro

in small cells:

12  
€
-->
12 €

def number_to_euro(amount)
  number_to_currency(amount,:unit=>'€').gsub(' ',nbsp)
end