Flowdock

Notes posted to Ruby on Rails

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February 23, 2009 - (<= v2.2.1)
1 thank

You can't have many :through with habtm

Imagine the following

a has_many b
b has_and_belongs_to_many c
a has_many c :through => b

a.b works fine

b.c works fine

a.c throws an error!

has_many :through where the through association is a habtm is not supported in Rails. The error is:

ActiveRecord::HasManyThroughSourceAssociationMacroError: Invalid source reflection macro :has_and_belongs_to_many for has_many :stories, :through => :subcategories. Use :source to specify the source reflection

Specifying the source reflection still won’t help you though, because this kind of has_many :through isn’t supported at all.

February 23, 2009 - (>= v2.0.0)
4 thanks

Nested with_options

You can nest with_options blocks, and you can even use the same name for the block parameter each time. E.g.:

class Product
  with_options :dependent => :destroy do |product|
    product.with_options :class_name => 'Media' do |product|
      product.has_many :images, :conditions => {:content_type => 'image'}
      product.has_many :videos, :conditions => {:content_type => 'video'}
    end

    product.has_many :comments
  end
end
February 23, 2009
2 thanks

Check if value is included in array of valid values

If you want to check the value of an attribute using an array of valid values, the array has to be defined before the validation, so

validates_inclusion_of :name, :in => VALID_NAMES
VALID_NAMES = %w(Peter Paul Mary)

won’t work, but

VALID_NAMES = %w(Peter Paul Mary)
validates_inclusion_of :name, :in => VALID_NAMES

will.

February 22, 2009
3 thanks

CAUTION! :frequency option description is misleading

To use event-based observer, don’t supply :frequency param at all. :frequency => 0 causes JS error.

Use this option only if time-based observer is what you need.

February 20, 2009
5 thanks

Static and dynamic attachments

You can attach static files directly:

attachment :content_type => "image/jpeg", :body => File.read("someimage.jpg")

and you can also define attachments dynamically by using a block:

attachment "text/csv" do |a|
  a.body = my_data.to_csv
end
February 18, 2009
4 thanks

Turn off for individual controllers/actions

To disable protection for all actions in your controller use skip_before_filter:

skip_before_filter :verify_authenticity_token

You can also pass :only and :except to disable protection for specific actions, e.g:

skip_before_filter :verify_authenticity_token, :only => :index
February 17, 2009
4 thanks

Date_select with assert_valid_keys

If you are using date_select with assert_valid_keys you have to allow 3 parameters named field(1i), field(2i) and field(3i).

For example with field

date_select("post", "written_on")

You have to allow following fields:

params[:post].assert_valid_keys( 
  'written_on(1i)', 'written_on(2i)', 'written_on(3i)'
)
February 17, 2009
9 thanks

Empty elements

If you want to output an empty element (self-closed) like “br”, “img” or “input”, use the tag method instead.

February 17, 2009
2 thanks

Remember to sanitize name

While useful when in need of richer markup inside a link, the name parameter isn’t sanitized or escaped and thus should be escaped when its content can’t be guaranteed to be safe.

E.g.

link_to(url, url)

may cause problems with character entities if url contains ampersands.

Correct usage
link_to(h(url), url)

This applies to all dynamic content.

February 17, 2009
1 thank

See column

See the end part of the docs on column for example uses.

February 16, 2009
1 thank

Reverse of this

If you want to do the reverse of this, e.g. go from a specific date and back to a certain day of the previous week, you can implement it like this:

def last_week(day = :monday)
  days_into_week = { :monday => 0, :tuesday => 1, :wednesday => 2, :thursday => 3, :friday => 4, :saturday => 5, :sunday => 6}
  result = (self - 7).beginning_of_week + days_into_week[day]
  self.acts_like?(:time) ? result.change(:hour => 0) : result
end

If you do not want to make your own method of this, but just want to do it in a regular chaining of date methods (like Date.today.next_year.at_midnight), you can do it like the following:

(date - 7).next_week(:tuesday) # Tuesday, last week

Please note that you just need to subtract 7 if you want to move back a week. Only use these methods if you want to go to a specific day of the week.

February 16, 2009
1 thank

Reverse naming

The reverse of this is last_month and not previous_month, like one might believe from the naming.

February 16, 2009
1 thank

Reverse naming

The reverse of this is last_year and not previous_year, like one might believe from the naming.

February 15, 2009
0 thanks

use #collect instead of #each

The earlier reminder to use #collect instead of #each applies regardless of whether the tag is nested or not.

This is counterintuitive, as #collect returns an array of strings of HTML tags, but ActionView renders it properly.

February 14, 2009
1 thank

Clear and simple rescue

noxyu3m, your code is rescuing all exceptions, not just ActiveRecord::RecordInvalid.

I think this syntax is a bit more clear than using the global variable.

def create
  @model = Model.new(params[:model)
  @model.save!
rescue => err                          # rescues all exceptions
  logger.error(err.to_s)
end
February 14, 2009
0 thanks

Simple rescue

Take it easy:

def create
  @model = Model.new(params[:model)
  @model.save!
rescue
  logger.error(!$.to_s)
end

Global variable !$ refers to the Exception object.

February 13, 2009
1 thank

throws exception

when use use Model.find([1,2,3,4])

throws exception if no record exists with any of this ID

February 13, 2009
3 thanks

New test syntax

You can use either one and even mix in the same test case if you want:

class Test < Test::Unit::TestCase
  # old way to define a test method (prefix with test_)
  def test_should_be_valid_without_content
    assert Comment.new.valid?
  end

  # new way to define a test
  test "should be valid without content" do
    assert Comment.new.valid?
  end
end
February 12, 2009
0 thanks

using collection=objects

It will fire one insert query per new record

February 10, 2009
8 thanks

Security issue with non-HTML formats

Please note that using default to_xml or to_json methods can lead to security holes, as these method expose all attributes of your model by default, including salt, crypted_password, permissions, status or whatever you might have.

You might want to override these methods in your models, e.g.:

def to_xml
  super( :only => [ :login, :first_name, :last_name ] )
end

Or consider not using responds_to at all, if you only want to provide HTML.

February 10, 2009
2 thanks
February 9, 2009
5 thanks
February 9, 2009
1 thank

:foreign_type option

I’m not sure if this has always been around but in 2.3, belongs_to takes a :foreign_type option on polymorphic associations. This behaves the same way as :foreign_key but for the type field.

February 7, 2009 - (>= v2.2.1)
1 thank

Documentation

Good docs can be found here: http://www.artweb-design.de/2008/7/18/the-ruby-on-rails-i18n-core-api

See also: http://rails-i18n.org/wiki for an extensive list of resources.

February 7, 2009 - (>= v2.2.1)
3 thanks

Deprecated

This method is deprecated. You should use:

I18n.translate('activerecord.errors.messages')
February 6, 2009 - (>= v2.1.0)
1 thank

Whacky edge case

The above works great as long as you select the primary key of the owning assocations.

preload_associations calls a group_by on that object so if there is no primary key attributed filled out it will reduce the records to 1 object. ex: rows = foo.find(:all,:select=>“boo.id, foo.name, foo.age, count(DISTINCT foo.id)”, :group=>“foo.name,foo.age having count( DISTINCT foo.id) > 1”,:joins=>“INNER JOIN bar.foo on bar.foo_id = foo.id”)

preload_assications(rows,:bar)

rows.first.bar.name #=> sql call already made in preload rows.last.bar.name #=> just made another sql call to get bar

fix: :select=>“foo.id, boo.id, foo.name, foo.age, count(DISTINCT foo.id)”

now preload_associations will include all the ids found instead of just the 1st one.

February 4, 2009
1 thank

How I use Optimistic Locking

I have used Optimistic locking often, but usually I only need it in one or two places in the codebase, not everywhere an object is saved whose model has a lock_version column. So what I usually end up doing is using a little module I wrote called OptimisticallyLockable (awesome name right?). Here it is:

module OptimisticallyLockable

  def self.included(receiver)
    receiver.lock_optimistically = false
    receiver.class_eval do

      def self.with_optimistic_locking
        original_lock = self.lock_optimistically
        self.lock_optimistically = true

        begin
          yield
        ensure
          self.lock_optimistically = original_lock
        end
      end

    end
  end

end

When included in a model that has a lock_version column it will turn off optimistic locking. Then when you want to actually use optimistic locking you can just use the with_optimistic_locking method like this:

class Blog
   include OptimisticallyLockable

   def do_something_destructive!
     self.class.with_optimistic_locking do
        #  do something important here
     end
   end                                
end