For performance improvements (and to remove the need for eager loading), the ActsAsTaggableOn gem supports caching your tag lists directly in your model. To enable this, simply add a cached_tag_list column to your table.

Example:

class Company < ActiveRecord::Base
  acts_as_taggable_on :categories
end

The cache column has to be named cached_category_list.

Existing data

If you already have existing data, you have to save all records with tags once, after you've added the ...

When you have objects in your database that hold latitude and longitude and you want to find others that are close to given coordinates you can use the Graticule gem.

Graticule

Graticule offers several methods to compute the distance between two geo-dated objects but fetching records from the database that are within a given radius of a location is a bit trickier:

def close_destinations(latitude, longitude)
  distance_sql = Graticule::Distance::Spherical.to_sql(:latitude => l...

Instead of running all missing migrations on your test database with rake db:migrate RAILS_ENV=test you can also use a handful of rake tasks to prepare the database structure directly. They can produce different results, though.

In a nutshell, to ensure your test database gains the correct structure:

• Don't use rake db:test:prepare carelessly
• or use rake db:test:clone_structure ← preferred :)
• or use rake db:migrate RAILS_ENV=test and don't mix it with other ways, like some of the rake tasks.

rake db:test:prepare
------------...

When using state_machine you sometimes need to know whether an object may execute a certain transition. Let's take an arbitrary object such as a blog article as an example that has those states:

A -> B -> C -> D

Additionally, you have transitions between the states as shown above. Let's call the transition between 'A' and 'B' transition_ab for simplicity. \
Given an object in state 'A'. You can call object.transition_ab but calling object.transition_bc! will obviously fail because ...

• Forms with many inputs (600+ in my case) become extremely unresponsive on an iPad, up to the point where it can take several seconds for a control to respond to touch commands.
• This is true for both iPad 1 and iPad 2 models.
• While certain CSS styles can lead to performance issues, removing those styles won't help if the form simply is very large.
• A workaround is to only show a limited number of form inputs at the time, e. g. by toggling groups of form...

Two new methods on and off are the new way of declaring event handlers. bind, delegate and live area deprecated. Also better performance for delegated events.

Note: This applies specifically to MySQL. In PostgreSQL for example, this is not an issue.

If you care about performance, never use a query like

UPDATE users SET has_message = 1 WHERE users.id IN (SELECT user_id FROM messages)

MySQL does not optimize this and seems to scan the temporary table, which isn't indexed, for every row in the update statement. This applies to other statements than UPDATE as well.

Instead, either use a JOIN like

UPDATE users INNER JOIN messages ON messages.user_id = users.id SET has_message =...

Clearance is a gem that provides authentication functionality (e.g. login, logout). This note explains, how the clearance login, logout and (in old Clearances) remember me functionality works.

Login

Clearance defines a database column called "remember_token". When you login in, that token will be saved in a cookie. For that reason you don't have to re-sign-in when you close and open the browser again.
This also means that you can be logged in in more than a single browser. Also see [When ses...

Look here for informations how you can show the MySQL default character set.

At first you need the Amazon RDS Command Line Toolkit

• download and unzip the [Amazon RDS Command Line Toolkit](http://aws.amazon.com/developertools/A...

Web fonts are awesome. After being restricted to Arial for two decades there is finally a cross-browser way to embed fonts into web pages.

Unfortunately while web fonts look awesome on Linux and MacOS, they look horrible on Windows, a problem that gets worse with smaller font sizes.

The culprit is something called font hinting:

...

To show the collation of your tables you have to login to the MySQL console and execute SHOW TABLE STATUS FROM database;

mysql> SHOW TABLE STATUS FROM test;
+-------------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+-----------------+----------+----------------+---------+
| Name        | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_leng...

You can convert git commits into patch files. Those can be used to apply to a different repository [1] or by someone else (e.g. sent when sent to them via e-mail).

Creating a patch in git

1. Make your changes and commit them.
2. Run git format-patch COMMIT_REFERENCE to convert all commits since the referenced commit (not including it) into patch files.

For example, let's say you prepared 2 commits. Run:

git format-patch HEAD~~ 

This will create 2 files, one for each commit since HEAD~~, like these:

00...

First keep in mind that :dependent => :destroy hooks into before_destroy.
So when you use other before_destroy callbacks the sequential arrangement of your code may be important.

For example:

class Container < ActiveRecord::Base
  before_destroy :a_callback
  has_many :items, :dependent => :destroy
end

results in

container.destroy
# => a_callback
# => container.items.destroy_all

but

class Container < ActiveRecord::Base
  has_many :items, :dependent => :destroy
  before_...

Using the jQuery adapter breaks the built-in save function of CKEditor.

Phenomenon: The page is submitted correctly, but the original values of the form fields were posted instead of what was typed in the editors.

Work around: Basicly instead of initiating the editor using the above example I ended up using the following:

$( 'textarea.editor').each( function() {

    CKEDITOR.replace( $(this).attr('id') );

});

Note: This assumes that each field using the editor has its own unique ID.

The Rails logger will store its content in a buffer and write it into the file system every 1000 lines. This will come back to bite you when using Rails.logger.info to write log output during Rake tasks or on a production console.

You often won't notice this because for the development and test environments auto_flushing is set to write after each line. On production environments the Rails logger writes only every 1000 lines -- and not upon shell or script ter...

Given the problem you have a new column postion and that column should be updated for all existing rows with ascending numbers. Furthermore these numbers should be generated by a special order. In order to achieve that you could do the following:

execute "SET @pos := 0;"
update " UPDATE pages SET position = ( SELECT @pos := @pos + 1 ) ORDER BY updated_at DESC;"

Single step and slow motion for Cucumber scenarios can come in handy, especially in @javascript scenarios.

# features/support/examiners.rb
AfterStep('@slow_motion') do
  sleep 2
end

AfterStep('@single_step') do
  print "Single Stepping. Hit enter to continue"
  STDIN.getc
end

If you're using spreewald, these tags are available as @slow-motion and @single-step (with dashes instead of underscores).

Note: You can also [prevent the selenium webbrowser wind...

In order to open a MySQL shell without the need to enter user and password, you can say the following in any Rails 2 project:

script/dbconsole -p

In Rails 3 you can say:

rails dbconsole -p

If you'd like to enter a database for an environment other than development you can say:

script/dbconsole -p staging

The technique described in this card has an important caveat: The result of GROUP_CONCAT is truncated to the maximum length that is given by the group_concat_max_len system variable, which has a default value of 1024. This will cause horrible, data-destroying bugs in production. For this reason you should probably not use GROUP_CONCAT ever. At least you must set the value of group_concat_max_len to an insanely high value on every database server your application runs on.

Lik...

You can use heredoc to avoid endlessly long lines of code that nobody can read. Heredoc strings preserve linebreaks and can be used like this:

def long_message
  puts(<<-EOT)
    Here goes a very long message...
    Sincerely,
    foobear
  EOT
end

<<-EOT will be somewhat of a placeholder: anything you write in the line after you used it will be its value until you write EOT in a single line.

You can use any string to flag your heredocs. To be more verbose you...

When you run rake db:create and get this error message

Couldn't create database for {"encoding"=>"utf8", "username"=>"root", "adapter"=>"mysql", "database"=>"project_development", "password"=>"topsecret"}, charset: utf8, collation: utf8_unicode_ci (if you set the charset manually, make sure you have a matching collation)

make sure the user you have specified (root/topsecret) in your database.yml has access to MySQL. You can check this by running mysql -uroot -p.

Most likely you run rake and your code is causing an exception which is not the one shown in your terminal.

Rails tries to catch this exception and clean up constants but -- while it's still booting up -- fails on this which causes another exception:

rake aborted!
cannot remove Object::ClassMethods

Running rake with the --trace parameter will give you no love; the backtrace is useless in most cases.

Try these approaches:

First: Check if there is a helpful error message

• Ha...

Here is a way to create a duplicate of one database, with all its tables and their data, under a new name.

1. Make a dump of your source database:

   mysqldump -uroot -p my_project -r my_project.sql
   

   Or, if you only want to dump the database's table structure (schema) without any contents:

   mysqldump -uroot -p my_project -r my_project.sql --no-data
   

2. Open up a MySQL shell:

   mysql -uroot -p
   

3. From the MySQL shell, create a new database and populate it with the dumped data:

   CREATE DATABASE my_project_copy;
   

...