Notes posted to Ruby on Rails

STI - Making callbacks trigger in inherited classes

Assuming we have

class ParentClass < ActiveRecord::Base
   attr_accessible :type
end

class ChildClass < ParentClass
   after_save :perform_something
end

Executing

ParentClass.create({:type => "ChildClass"})

will not trigger ChildClass callbacks. What is more, it will return instance of ParentClass instead of ChildClass.

To resolve this issue, you need to define following module

module ActiveRecord
  module CallbacksAwareSti
    extend ActiveSupport::Concern
    module ClassMethods
      def new(*args, &block)
        return super(*args, &block) unless args.first.respond_to?(:with_indifferent_access)
        type = args.first.with_indifferent_access[:type]
        if type.blank? or (type = type.constantize) == self
          super(*args, &block)
        else
          super(*args, &block).becomes(type)
        end
      end
    end
  end
end

and include it in parent class

class ParentClass < ActiveRecord::Base
   include ActiveRecord::CallbacksAwareSti
   attr_accessible :type
end

Inspired by http://stackoverflow.com/questions/4518935/activerecord-problems-using-callbacks-and-sti

block only and except

Code

class Journal < ActionController::Base
  # Require authentication for edit and delete.
  before_filter :authorize, :only => [:edit, :delete]

  # Passing options to a filter with a block.
  around_filter(:except => :index) do |controller, action_block|
    results = Profiler.run(&action_block)
    controller.response.sub! "</body>", "#{results}</body>"
  end

  private
    def authorize
      # Redirect to login unless authenticated.
    end
end

Hidden Field Example

Here’s a pseudo code example of a hidden field within an ERB template. A post has many comments and this comment form is in a post’s show view. This would set a comment’s post_id attribute.

<%= form_for(@comment) do |f| %>

<%= f.hidden_field :post_id, :value => @post.id %>

<% end %>

method to use instead

This may be obvious, but the replacement for this method is csrf_meta_tags.

Example from Code School

module Tweets

 class ShowPresenter
   extend ActiveSupport::Memoizable

   def initialize(tweet)
     @tweet = tweet
   end

   def username
     @tweet.user.username
   end

   def status
     @tweet.status
   end

   def favorites_count
     @tweet.favorites.count
   end

   memoize :username, :status, :favorites_count

 end
end

From http://railsbest.com/

MUCH easier way to pluralize without the number...

Just use Ruby!

"string".pluralize(count)

HTML5 data- attributes using RESTful approach

HTML5 specifies extensible attributes like data-foo=“bar” (or as in Twitter Bootstrap data-toggle=“modal”), which poses two problems for Rails.

First, if you’re using symbol notation in link_to to specify attributes, this fails (dash is not a valid symbol character), so

Invalid!

link_to "Edit", @user, :class => "btn", :data-toggle => "modal"

There are two solutions:

1. put the symbols in quotes,

2. use the special :data hash

Solution 1: Quote Symbols

link_to "Edit", @user, :class => "btn", "data-toggle" => "modal"

Solution 2: Use the :data hash

link_to "Edit", @user, :class => "btn", :data => {:toggle => "modal"}

Resulting HTML

<a href="/users/1" class="btn", data-toggle="modal">Edit</a>

The second is minimally documented, but as a hash, can accept multiple values and is perhaps a little cleaner

I got it

Perfect match to work with attr_accessible

Locale

To change default locale by the parameter you can set :locale option, like below:

select_date 'user', 'birth', :locale => 'de'

Missed close tag

At the page http://apidock.com/rails/ActionView/Helpers/TagHelper/tag

<tt>.data()</tt> should be instead of <tt>.data()<tt>

Looks like this method has trouble with attributes:

ex:

require 'rubygems'
require 'bundler'
require 'active_support/core_ext'
require 'pp'

xml  = 
  '<test id="appears">
    <comment id="doesnt appear">
      it worked
    </comment>
    <comment>
     see!
    </comment>
    <comment />
  </test>'

hash = Hash.from_xml(xml)

pp hash

#=>{"test"=>{"id"=>"appears", "comment"=>["it worked", "see!", nil]}}

# Notice how the id attribute on the first comment element doesn't appear.

Rails 3 TimeZone

It’s over at http://apidock.com/rails/ActiveSupport/TimeZone/new/class

Options select_hour

In my view I wanted to do this <%= select_hour(@hour, :start => 8, :end => 12) %> but did not work. I looked at the documentation and have not seen anything like it. http://api.rubyonrails.org/classes/ActionView/Helpers/DateHelper.html#method-i-select_hour

So I studied how it worked this helper. http://api.rubyonrails.org/classes/ActionView/Helpers/DateHelper.html#method-i-select_hour develop and achieve this:

the helper application:

module DataAnnouncementsHelper

class HelperDate < ActionView::Helpers::DateTimeSelector
  def select_hour
    if @options[:use_hidden] || @options[:discard_hour]
      build_hidden(:hour, hour)
    else
      build_options_and_select(:hour, hour, :end => @options[:end], :start => @options[:start], :ampm => @options[:ampm])
    end
  end
end

def select_hour(datetime, options = {}, html_options = {})
   HelperData.new(datetime, options, html_options).select_hour
end

end

The view:

<%= select_hour(@hour, :start => 8, :end => 12) %>

Where @hour = 10 the result is:

<select id=“date_hour” name=“date[hour]”>

<option value="08">08</option>
<option value="09">09</option>
<option value="10" selected="selected">10</option>
<option value="11">11</option>
<option value="12">12</option>

</select>

JQuery script for dynamically adding and removing fields_for

I like drogus idea. But I wanted a cleaner one, so I created an unobtrusive JQuery script to have the same functionality.

Example Usage:

<%= form_for @post do |form| %>
  Title: <%= form.text_field :title %>
  Body: <%= form.text_field :body %>

  Tags:
  <div id="tag-list"></div>

  <div class="numerous">
    <div class="numerous-form">
      <%= form.fields_for :tag, Tag.new, :child_index => "replace_this" do |f| %>
        <%= f.text_field :name %>
        <%= f.hidden_field :_destroy, :value => 0, :class => "numerous-remove-field" %>
        <%= link_to "delete", "#", :class => "numerous-remove" %>
      <% end %>
    </div>

    <%= link_to "add tag", "#", :class => "numerous-add", :id => "for-tag-list" %>
  </div>
<% end %>

See script at: http://github.com/kbparagua/numerous.js

:as option

Code

root :to => 'projects#index', :as => 'foobar'

will generate a helper

foobar_path

Disable layout on ajax

In actions that may or may not be loaded via ajax I use:

render :layout => !request.xhr?

For an entire controller I might use something like:

layout :has_layout?

private
  def has_layout?
    request.xhr? ? false : controller_name
  end

What seems unusual is that

layout true

will try look for the layout true.erb

Replaced by

replaced by “class_attibute”: http://apidock.com/rails/v3.2.1/Class/class_attribute

Replaced by

replaced by “class_attibute”: http://apidock.com/rails/v3.2.1/Class/class_attribute

Makes it possible to use a scope through an association

This is a very useful method if you want to to use a scope through an association:

class Book < ActiveRecord::Base
  scope :available, where(:available => true)
end

class Author < ActiveRecord::Base
  has_many :books
  scope :with_available_books, joins(:books).merge(Book.available)
end

# Return all authors with at least one available book:
Author.with_available_books

See http://asciicasts.com/episodes/215-advanced-queries-in-rails-3 for more info.

Reorder

If you want to override previously set order (even through default_scope), use reorder() instead.

E.g.

User.order('id ASC').reorder('name DESC')

would ignore ordering by id completely

Example to auto download

Controller

op = Operation.find(params[:id])
fname = "operation_#{op.id}_#{DateTime.now.to_i}.csv"
send_data op.export(params[:url_type]), 
  :type => 'text/csv; charset=iso-8859-1; header=present',
  :disposition => "attachment; filename=#{fname}.csv"

export_csv

def export(url_type)
  csv_data = CSV.generate do |csv|
    csv << self.header_columns # simple array ["id","name"]
    url_items = @operation.url_items.where(:url_type => url_type)
    url_items.each do |url_item|
      csv << self.process_row(url_item)  # simple array [1,"bob"]
    end 
  end 
  return csv_data
end

Use exist scopes on default_scope - pay attention

To use exists scopes on default_scope , you can use something like:

class Article < ActiveRecord::Base
  scope :active, proc {
    where("expires_at IS NULL or expires_at > '#{Time.now}'")
  }

  scope :by_newest, order("created_at DESC")

  default_scope by_newest
end

But, if you would add a filter, and it require a lazy evaluate, use block on default_scope declaration, like:

default_scope { active.by_newest }

Deprecation in 3.1+

In Rails 3.1 and higher, just use ruby’s SecureRandom, e.g.

Before

ActiveSupport::SecureRandom.hex

After

SecureRandom.hex

Deprecated proxy_owner

Just change your

proxy_owner

calls to

@association.owner

Found it here: http://mileszs.com/deprecation-warnings-for-proxyowner-in-rails

Add html5 scriipt async attribute

http://www.w3schools.com/html5/att_script_async.asp

javascript_include_tag "application", :async => true

flash messages

In rails 3.1 the following does not work for me

redirect_to { :action=>'atom' }, :alert => "Something serious happened" 

Instead, you need to use the following syntax (wrap with parens)

redirect_to({ :action=>'atom' }, :alert => "Something serious happened")

Example of conditions using

f.e.

validates :number, :presence => { :if => :quota_file? }

def self.quota_file?
  quota_file?
end

won't refresh updated_at

This will not cause :updated_at column to refresh, while ActiveRecord::Base#increment! would.

looking to bypass validations, callbacks and updated_at?

Take a look at updated_column

http://apidock.com/rails/ActiveRecord/Persistence/update_column

How to user method 'from'

example

User.from('posts').to_sql
# => "SELECT `users`.* FROM posts"