Flowdock

Recent notes

RSS feed
October 7, 2010 - (>= v3.0.0)
1 thank

Custom validator with i18n support

Here is modified EmailValidator from the example above:

class EmailValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    record.errors.add(attribute, options[:message] || :email) unless
      value =~ /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i
  end
end

And locale:

en:
  activerecord:
    errors:
      messages:
        email: "is not an email"
October 4, 2010
1 thank

Bind the named method to the receiver

Binds the named method to the receiver, returning a Method object with access to the internals of the receiver, such as self and instance variables.

September 29, 2010
1 thank

Anchor option

It’s not documented, but :anchor is an option.

polymorphic_path(commentable, :anchor => 'comments')

will return:

/article/1#comments
September 29, 2010 - (v3.0.0)
1 thank

Mistake in example for Rails 3

This code doesn’t work:

activemodel:
  attribute:
    post:
      cost: "Total cost"

Everything is OK with this one:

activerecord:
  attributes:
    post:
      cost: "Total cost"
September 27, 2010
0 thanks

Nice german translation independet of structure of a sentence

Eine pragmatische Lösung für das Übersetzungsproblem der Rails Methode distance_of_time_in_words(). Im Deutschen wird je nach Satzbau eine andere Ausgabe benötigt.

Vor mehr als 5 Monaten“/”Vor etwa einem Jahr“ — statt wie im Original ”Dauer: mehr als 5 Monate“/”Dauer: etwa 1 Jahr

http://gist.github.com/598965

September 23, 2010
0 thanks

Or maybe...

or maybe

add_index :user_follows , :user
add_index :user_follows , :followed_user
September 22, 2010
1 thank

About the options argument

The options are not documented, but of course you can use the same options than submit_tag.

Note that all non-documented options are simply passed to the input tag. Amongst other things, this allows you to change the default name attribute (commit):

form.submit 'Cancel', :name => 'cancel'

That’s very handy in forms with multiple submit buttons, this way the controller can easily check in the params which action was submitted.

September 21, 2010
1 thank

using joins, group, having

Code example

named_scope :red, :joins =>   [:color_lis => :color], :group => "color.id", :having => ["color.xx IS NULL"]
September 17, 2010 - (<= v2.3.8)
1 thank

No Layout (fixed typo)

@wiseleyb: Seems to be a typo, should be:

render_to_string(:action => "users/profile", :layout => false)
September 17, 2010
0 thanks
September 16, 2010
1 thank

Re: Doesn't work? Don't think it ever has.

Instead of

create_table :user_follows, :force => true do |t|
  t.references :user
  t.references :followed_user
  t.timestamps
  t.index :user
  t.index :followed_user
end

Try

create_table :user_follows, :force => true do |t|
  t.references :user
  t.references :followed_user
  t.timestamps
end

index :user_follows , :user
index :user_follows , :followed_user

It looks like the provided examples are incorrect…

September 13, 2010 - (>= v1.0.0)
2 thanks

No concurrency

If you want to handle concurrency, this doesn’t work:

a = Article.first
b = Article.first
a.increment!(:view_count)
b.increment!(:view_count)
a.reload.view_count # -> 1
b.reload.view_count # -> 1

Instead, use SQL:

def increment_with_sql!(attribute, by = 1)
  raise ArgumentError("Invalid attribute: #{attribute}") unless attribute_names.include?(attribute.to_s)
  original_value_sql = "CASE WHEN `#{attribute}` IS NULL THEN 0 ELSE `#{attribute}` END"
  self.class.update_all("`#{attribute}` = #{original_value_sql} + #{by.to_i}", "id = #{id}")
  reload
end
September 9, 2010
1 thank

bad idea.

Just a note, ypetya’s idea of using a before filter to set the primary key wont scale. transactions will eventually step on each other and probably end up with duplicate key ids, unless you have some other method to ensure uniqueness.

You’d be better off using mysql to generate the default integer primary key and have a secondary string “key” field.

September 9, 2010
0 thanks

Doesn't work? Don't think it ever has.

This doesn’t work for me. I do something like:

create_table :user_follows, :force => true do |t|
  t.references :user
  t.references :followed_user
  t.timestamps
  t.index :user
  t.index :followed_user
end

and I get:

rake aborted!
An error has occurred, all later migrations canceled:

undefined method `index' for #<ActiveRecord::ConnectionAdapters::TableDefinition:0x106c02220>

add_index has the same effect.

September 9, 2010
1 thank

takes ActiveRecord object as an arg as well

One undocumented feature, you can do this:

person = Person.first
Person.exists?(person)
# => returns true

This came in handy for me when I needed to see if something belonged to a particular scope.

scope = "created_rails"
person = Person.find_by_name "dhh"
Person.send(scope).exists?(person)
# => returns true

Obviously this relies on you having a named_scope in your Person model called “created_rails”.

September 7, 2010 - (v1_8_6_287 - v1_8_7_72)
1 thank

To illustrate Date class let's calculate days between dates

Code example

date_from = Date.new(2010, 9, 11)
#<Date: 4910901/2,0,2299161>
date_till = Date.new(2010, 11, 12)
#<Date: 4911025/2,0,2299161>
rational_offset = (date_till - date_from)
#Rational62, 1
rational_offset.to_i
#62
September 3, 2010
0 thanks

Don't forget about as

:as is a good but poorly document argument to rendering a collection:

<%= render :partial => 'some_partial', :collection => an_array, :as => :better_name -%>

Which will give you each element of an_array in the partial in a local variable named better_name not some_partial.

September 2, 2010
0 thanks

Set hour and/or minutes

To set the hour and/or the minutes, you can use:

<%= f.datetime_select(:offer_end, :default => { :hour => 23, :minute => 59 }) %>
August 25, 2010 - (>= v2.3.8)
9 thanks

Undocumented :inverse_of option

Support for the :inverse_of option was backported to 2.3.6+.

Here’s the description from the original commit: http://github.com/rails/rails/commit/ccea98389abbf150b886c9f964b1def47f00f237


You can now add an :inverse_of option to has_one, has_many and belongs_to associations. This is best described with an example:

class Man < ActiveRecord::Base
  has_one :face, :inverse_of => :man
end

class Face < ActiveRecord::Base
  belongs_to :man, :inverse_of => :face
end

m = Man.first
f = m.face

Without :inverse_of m and f.man would be different instances of the same object (f.man being pulled from the database again). With these new :inverse_of options m and f.man are the same in memory instance.

Currently :inverse_of supports has_one and has_many (but not the :through variants) associations. It also supplies inverse support for belongs_to associations where the inverse is a has_one and it’s not a polymorphic.

August 25, 2010 - (>= v2.3.8)
2 thanks

Undocumented :inverse_of option

Support for the :inverse_of option was backported to 2.3.6+.

Here’s the description from the original commit: http://github.com/rails/rails/commit/ccea98389abbf150b886c9f964b1def47f00f237


You can now add an :inverse_of option to has_one, has_many and belongs_to associations. This is best described with an example:

class Man < ActiveRecord::Base
  has_one :face, :inverse_of => :man
end

class Face < ActiveRecord::Base
  belongs_to :man, :inverse_of => :face
end

m = Man.first
f = m.face

Without :inverse_of m and f.man would be different instances of the same object (f.man being pulled from the database again). With these new :inverse_of options m and f.man are the same in memory instance.

Currently :inverse_of supports has_one and has_many (but not the :through variants) associations. It also supplies inverse support for belongs_to associations where the inverse is a has_one and it’s not a polymorphic.

August 25, 2010 - (>= v2.3.8)
7 thanks

Undocumented :inverse_of option

Support for the :inverse_of option was backported to 2.3.6+.

Here’s the description from the original commit: http://github.com/rails/rails/commit/ccea98389abbf150b886c9f964b1def47f00f237


You can now add an :inverse_of option to has_one, has_many and belongs_to associations. This is best described with an example:

class Man < ActiveRecord::Base
  has_one :face, :inverse_of => :man
end

class Face < ActiveRecord::Base
  belongs_to :man, :inverse_of => :face
end

m = Man.first
f = m.face

Without :inverse_of m and f.man would be different instances of the same object (f.man being pulled from the database again). With these new :inverse_of options m and f.man are the same in memory instance.

Currently :inverse_of supports has_one and has_many (but not the :through variants) associations. It also supplies inverse support for belongs_to associations where the inverse is a has_one and it’s not a polymorphic.

August 25, 2010 - (>= v2.3.8)
3 thanks

Validating presence of parent in child

When creating a parent and its children using nested attributes, you can use the :inverse_of option on the association to correctly set the parent back references:

class Parent < ActiveRecord::Base
  has_many :children, :inverse_of => :parent
  accepts_nested_attributes_for :children
end

class Child < ActiveRecord::Base
  belongs_to :parent
  validates_presence_of :parent
end
August 24, 2010 - (>= v2.3.2)
0 thanks

Deprecated

Instead of using:

session.delete

Now use:

reset_session
August 17, 2010
1 thank

Getting n..end in Rails

Nice one, henning. For anyone using Rails (ActiveSupport) a handy method called #from is also present.

[1, 2, 3, 4, 5].from(2) # => [3, 4, 5]

So our example would be

a.from(i)

It reads a lot better

August 16, 2010
0 thanks

update_all and serialized attributes

If you use update_all to change an attribute marked as serialized ( using ActiveRecord::Base.serialize ), you need to call to_yaml yourself:

User.update_all({ :preferences => { :first_name => 'John',
                                     :last_name  => 'Doe' }.to_yaml })
August 13, 2010
9 thanks

add_to_base in Rails 3

use

model_instance.errors[:base] << "Msg" 

instead of depracated

model_instance.errors.add_to_base("Msg")

for Rails 3

August 13, 2010
0 thanks

Depracated add_to_base

use

model_instance.errors[:base] << "Msg" 

instead of depracated

model_instance.errors.add_to_base("Msg")

for Rails 3

August 13, 2010
1 thank

Confusing log output

If you do a single Rails.cache.read('my_key'), your will usually see in your log something like

Cache read: my_key
Cache read: my_key
Cache write: my_key

Don’t worry about this.

What happens here is this: Before going to memcached, rails will first ask a local MemoryStore cache (which is responsible for the first and third line in the log), before falling through to memcached. This local cache is destroyed after each request.

Source is in activesupport/lib/active_support/cache/strategy/local_cache.rb.

August 11, 2010
3 thanks

In Rails3 use "unscoped" instead

The with_exclusive_scope examples no longer work in Rails3 because with_exclusive_scope is now a protected method which can and should not be used in a controller. Use the new unscoped method instead:

Article.unscoped

For mor details and examples have a look at: http://github.com/rails/rails/commit/bd1666ad1de88598ed6f04ceffb8488a77be4385.