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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

current_url

exact url from browser window:

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

October 25, 2008
3 thanks
October 24, 2008
11 thanks

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.

October 24, 2008
9 thanks

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.

October 23, 2008
8 thanks

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.

October 22, 2008
10 thanks

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.

October 21, 2008
5 thanks

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.

October 20, 2008
3 thanks

number_to_euro

in small cells:

12-->
12def number_to_euro(amount)
  number_to_currency(amount,:unit=>'').gsub(' ',nbsp)
end
October 15, 2008
29 thanks

List of status codes and their symbols

Note that the :status option accepts not only an HTTP status code (such as 500), but also a symbol representing that code (such as :created), if that makes more sense to you. Here’s a list of which symbols map to which numbers (derived from ActionController::StatusCodes::SYMBOL_TO_STATUS_CODE):

100 = :continue
101 = :switching_protocols
102 = :processing
200 = :ok
201 = :created
202 = :accepted
203 = :non_authoritative_information
204 = :no_content
205 = :reset_content
206 = :partial_content
207 = :multi_status
226 = :im_used
300 = :multiple_choices
301 = :moved_permanently
302 = :found
303 = :see_other
304 = :not_modified
305 = :use_proxy
307 = :temporary_redirect
400 = :bad_request
401 = :unauthorized
402 = :payment_required
403 = :forbidden
404 = :not_found
405 = :method_not_allowed
406 = :not_acceptable
407 = :proxy_authentication_required
408 = :request_timeout
409 = :conflict
410 = :gone
411 = :length_required
412 = :precondition_failed
413 = :request_entity_too_large
414 = :request_uri_too_long
415 = :unsupported_media_type
416 = :requested_range_not_satisfiable
417 = :expectation_failed
422 = :unprocessable_entity
423 = :locked
424 = :failed_dependency
426 = :upgrade_required
500 = :internal_server_error
501 = :not_implemented
502 = :bad_gateway
503 = :service_unavailable
504 = :gateway_timeout
505 = :http_version_not_supported
507 = :insufficient_storage
510 = :not_extended
October 10, 2008
7 thanks

Implemented in database adapters

These methods are not implemented in the abstract classes. Instead, all database adapters implement these separately, if the feature is supported.

October 9, 2008 - (v1.2.0 - v2.1.0)
12 thanks

Rendering nothing

If your controller action does not explicitly call render, Rails will, by default, attempt to locate and render the template corresponding to the action. It’s not uncommon, for example with Ajax calls, to want to render nothing. This will circumvent the default rendering and prevent errors on missing templates. To render nothing simply do the following:

render :nothing => true

Its important to note that this isn’t the same as returning no HTTP response. In fact, this results in an HTTP response with a status code of 200 OK being sent back with a blank content body. Why does it matter? Well, you can still test your controller by asserting that a :success response was returned.

October 9, 2008
6 thanks

Works with URLs too!

You can use it for web urls as well:

path, file = File.split('/uploads/art/2869-speaking-of-pic.jpg')
p path # => "/uploads/art"
p file # => "2869-speaking-of-pic.jpg"

And you can also use join, to merge url back from the components:

path = File.join(["/uploads/art", "2869-speaking-of-pic.jpg"])
p path # => "/uploads/art/2869-speaking-of-pic.jpg"

Using #join and #split for operations on files and path parts of the URLs is generally better than simply joining/splitting strings by ‘/’ symbol. Mostly because of normalization:

File.split('//tmp///someimage.jpg') # => ["/tmp", "someimage.jpg"]
'//tmp///someimage.jpg'.split('/') # => ["", "", "tmp", "", "", "someimage.jpg"]

Same thing happens with join.

October 8, 2008
3 thanks

Seriously! Do not forget the brackets

thank you source jamesandre.ws

the form_for([:admin, @user]) must have the [] brackets to avoid errors like “Only get requests are allowed”

<% form_for([:admin, @user]) do |f| %>
<%= render :partial => 'form' %>
<%= submit_tag "Create" %>
<% end %>
October 7, 2008 - (v2.0.3 - v2.1.0)
4 thanks

More on deprecation

This is not deprecated. I think the docs are confused because the validate, validate_on_create, and validate_on_update methods are actually callbacks and not explicitly defined on their own. The correct usage is the same as in the docs above.

October 2, 2008
8 thanks

:prefix option

Be aware!

By default, if you do select_month(Date.today, :field_name => ‘start’) it will generate select tag with name “date[start]”. If you want it to be something other than date[], add :prefix option, like this:

select_month(Date.today, :field_name => 'start', :prefix => 'timer')

This will render select tag with name “timer[start]”.

Taken from sources of name_and_id_from_options method.

October 1, 2008
5 thanks
September 30, 2008
5 thanks

If you're not using resource

If you don’t use resource for your remote_form_for, then :url option is necessary.

For example:

<% remote_form_for "not_resource" do |f| ... %> 

won’t work. But with :url option, it will:

<% remote_form_for "not_resource", 
     :url => { :controller => "recommend", :action => "send" } do ... %> 
September 28, 2008 - (v2.0.0 - v2.1.0)
3 thanks

has_one Nesting in Rails 2.0

Routers:

map.resources :user, :has_one => [:avatar]

Views:

form_for [@user, @avatar], :url => user_avatar_url(@user) do |f|
...
end
September 27, 2008
3 thanks

Example using simple_matcher

This is extracted from: http://blog.davidchelimsky.net/2008/6/7/thoughts-on-the-dance-off

Here’s an example:

def be_sorted
  simple_matcher("a sorted list") {|actual| actual.sort == actual}
end
[1,2,3].should be_sorted

The block is handed the actual value. If the block returns true, the expectation passes. If it returns false, it fails with the following message:

expected “a sorted list” but got [1, 3, 2]

If you say [1,2,3].should_not be_sorted you’d get this message instead=:

expected not to get “a sorted list”, but got [1, 2, 3]

As of now, you don’t get any control over the failure message other than the string you pass to the simple_matcher method

September 26, 2008 - (v1.2.6 - v2.1.0)
5 thanks

Pass the observed fields value as a parameter in the Ajax request

Use encodeURIComponent with with to pass an encoded value as a parameter (POST or GET) of the AJAX request. For example:

<%= observe_field :company_id,

:url => {:action => ‘facilities’, :only_path => false}, :with => “‘company=’ + encodeURIComponent(value)” %> Also, setting only_path => false for the URL ensures that the full URL (including host and protocol) is used for the AJAX request.

September 26, 2008
4 thanks

Example of composed_of composition class implementation

If we have following code in model:

composed_of :temperature, :mapping => %w(celsius)

Then our composition class can be this:

class Temperature
  def initialize(celsius)
    @celsius = celsius
  end

  # This method is called by ActiveRecord, when record is saved.
  # Result of this method will be stored in table in "celsius" field,
  # and later when the record is loaded again, this will go to 
  # our Temperature#new constructor.
  def celsius
    @celsius
  end

  # This is example of method that we can add to make this composition useful.
  def farenheit 
    @celsius * 9/5 + 32
  end
end
September 25, 2008
4 thanks

has_many :through

It’s is recommended to use has_many :through association instead of has_and_belongs_to_many. has_many :through is better supported and generally easier to work with once you grasp the idea.