So I had this problem with a record that was being saved even though it failed validation:

cc = CreditCard.new(:card_number => 'invalid')
>> cc.save
=> false
>> cc.id
=> 3

That one had me stumped for a while until I realized I was carelessly using update_attribute in my custom writer:

def card_number=(num)
  update_attribute(:crypted_card_number, encrypt(num))
end

And we all know that update_attribute “saves the record without going through the normal validation procedure.”

Everything worked much nicer after I changed the code to:

def card_number=(num)
  self.crypted_card_number = encrypt(num)
end

Pipes and Redirection

These are standard shell tools, but sometimes I get confused about which one I need. So my way of thinking about it is that pipes are a connection between programs while redirection always goes to (or from) a file.

So, for example, in order to find all my session routes I would connect the rake and grep commands via a pipe:

  rake routes | grep session

On the other hand, I would use redirection to save the output of a git diff to a file so as to be able to feed it in to the patch program (which expects its input on standard in).

  git diff > patchfile
  patch < patchfile

Braces

I just learned about these recently and they make renaming things so much easier!

  mv file.old file.new # old way
  mv file.{old,new} # does the same thing!

So creating your database.yml file from the example one is as easy as:

  mv config/database.yml{.example,}

Changing Directories

I assume everyone already knows that cd with arguments goes to your home directory (the contents of the $HOME environment variable), but did you know you can do 'cd -' to go to the previous directory you were in ($OLDPWD)?

  :/var/www$ cd /etc/apache2/sites-enabled/
  :/etc/apache2/sites-enabled$ cd -
  /var/www
  :/var/www$

History

!! # execute the previous command (great for when you forget to sudo something)
!$ # The last argument of the previous command
!^ # The first argument
!* # All the previous arguments
^old^new^ # Repeat the previous command replacing old for new

And lots, lots more! See 'man history' for details.

Keyboard shortcuts

Here are a few of the keyboard shortcuts that I use regularly (copied from the wikipedia article http://en.wikipedia.org/wiki/Bash):

CTRL + l : clears the screen content (equivalent to the command : clear).
CTRL + u : clears the line content before the cursor and copy it in the clipboard.
CTRL + k : clears thctrl alt copy pastee line content after the cursor and copy it in the clipboard.
CTRL + w : clears the word before the cursor and copy it in the clipboard.
CTRL + y : (yank) adds the clipboard content from the cursor position.

>> (19.99 * 100).to_i
=> 1998
>> (9.99 * 100).to_i
=> 999

Someone please tell me what’s up with that!

In the meantime:

>> (19.99 * 100).to_s.to_i
=> 1999

We ran into a few little gotchas with ActiveRecord’s find method when upgrading from Rails 2.1.1 to 2.2.2. The solutions are pretty trivial, so the main lesson here is to test your code so things like this get caught by your test suite and not the client.

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