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;
   

...

Observed on Rails 2.3 and machinist 1.0.6

Like the title says, when you define the method empty? like in the following example, you may not longer use collection.make.

class Book

  has_many :pages

  def empty?
    pages.empty?
  end

end

Assuming

b1 = Book.find(1)
b2 = Book.find(2)

instead of expected

b1.pages.make #=> #<Page id: 1, book_id: 1>
b2.pages.make #=> #<Page id: 2, book_id: 2>

you'll get

b1.pages.make #=> #<Page id: 1, book_id: 3>
b2.pages.make #=> #<Page id: 2,...

There is a bug in Rails 3's dbconsole script, which makes the following command open a database console for the development environment:

rails dbconsole -p test

You need to write this instead:

rails dbconsole test -p

Simple: Tell the application controller how to handle exceptions, here a RecordNotFound error.
Do this with the following line:

# application_controller.rb

  rescue_from ActiveRecord::RecordNotFound, :with => :render_404

This will call the method render_404 whenever a RecordNotFound error occurs (you could pass a lambda instead of a symbol, too).
Now write this method:

def render_404
  render 'errors/404', :status => '404'
end

Finally create a 404 document views/errors/errors.html.haml.

%h1 Record...

jQuery as new default Javascript library, streaming response support, attr_accessible with roles, prepared statements, easier migrations.

While it might seem trivial to implement an invoice that sums up items and shows net, gross and vat totals, it actually involves a lot of rules and caveats. It is very easy to create invoices where numbers don't add up and a few cents are missing. A missing cent is a big deal for an accountant, so it is important for your invoices to list correct numbers.

Note that this is not legal advice. Also note that while this note has a number of code examples in Ruby and MySQL, the concepts apply to all programming languages and data stores.

When ...

You've been there: A form cannot be submitted, but you don't see a validation error because the field at fault has no corresponding input field on the form. Because this is usually a bug, you insert debug information listing all errors into the form view. And once the bug is fixed, you forget to take out that debug information.

There is a better way. By copying one of the attached initializers into config/initializers, your forms will always render a small box listing all form errors in the bottom right corner of the screen. This box is n...

This is a bug in Timecop 0.3.4 or lower. You should upgrade to 0.3.5.

Did you return false in a before_validation callback?

I recently browsed through the ActiveSupport code and found some nice stuff I did not know about:

ActiveSupport::Callbacks

ActiveRecord-like callbacks, if you need callbacks in non ActiveRecord objects

ActiveSupport::MessageEncryptor

encrypt and decrypt ruby objects

[ActiveSupport::MessageVerifier](https://github.com/rails/rails/blob/mast...

When the Ruby parser module of Ruby-GetText comes across a file in one of its search directories (e.g. lib/scripts/) and finds out that you are defining ActiveRecord classes inside it, it evaluates the whole file. Here is how to avoid that.

What's happening?

Let's say you have the following script which is only run once, manually, via script/runner:

# lib/scripts/doomsday.rb
class User < ActiveRecord::Base; end
User.destroy_all

In that case we ...

Do you wonder which databases are actually taking up how much space but only have one huge ibdata1 in your /var/lib/mysql and the directories inside your mysql data directory don't represent the actual database sizes? This is for you!

Run from a mysql root console:

SELECT table_schema AS "Database name", SUM(data_length + index_length) / 1024 / 1024 AS "Size (MB)" FROM information_schema.TABLES GROUP BY table_schema;

This will get you a result like the following:

+----------------------+--------------+
| Database name    ...