Alexander Mikhailian

ActiveRecord is a beautiful piece of software. But just step aside of the prescribed road, and you are guaranteed to have problems.

This time, my problems began when I started to design the model first. I quickly laid out a couple of screens of objects, wrote the connection line and ran the code.

class SubjectLocator  "String"
end

# a dozen more objects follow...

ActiveRecord::Base.establish_connection(
  :adapter  => "mysql",
  :host     => "localhost",
  :username => "test",
  :password => "test",
  :database => "activerecord"
)

It has not come as a surprise that ruby replied with an exception.

Table 'activerecord.subject_locator' doesn't exist: SHOW FIELDS FROM `subject_locator` (ActiveRecord::StatementInvalid)

What surprised me is that after half an hour of search on the internet, I found no way to boostrap a DB schema out of the model. There were discussions on the rails mailing list. They even went as far as suggesting non-destructive automatic migrations, a feature that exists in Hibernate for at least 5 years already. None dared to implement either.

I am now left with one solution. Apply the DRY3 principle, aka "Do Repeat Yourself 3.times" and start writing the migrations script for my models (repeat!), as well as an SQL schema for my MySQL database that would keep indexes, views and triggers in addition to what I will boostrap from migrations (repeat again!)

Тут Лукьяненко поставил ссылку на высказывание об авторском праве Романа Афанасьева. Что симптоматично, у обоих комментарии отключены. К чему бы это?

ЗЫ: Назовите меня идиотом, но чтобы найти ссылку на этот постинг Лукьяненко, пришлось прошерстить 431 страничку, от id предыдущего постинга до id следующего. Примерно вот так:

for i in `seq 304622 305053`; do
wget http://doctor-livsy.livejournal.com/$i.html
done |grep gringrin *html

How can one not be disappointed with Groovy after looking at its User Guide?

Here is just one example. Can you tell from the StreamingMarkupBuilder documentation how it works? I bet no. After looking through the code snippets on the page and figuring out I could not understand a line of code there, I wondered what is the mkp variable that appears twice on the page.

It took me some time to get through the Groovy class hierarchy up to the BaseMarkupBuilder.java just to find the mkp namespace declaration.

 namespaces.put("mkp", "http://www.codehaus.org/Groovy/markup/keywords");   // pseudo namespace for markup keywords

After googling for mkp markup keywords, I found a page that explains in a few words the design of markup builders. Nothing more, nothing less. Now, I know everything I had to know about mkp and markup builders. The thing is, it is a post of the developer who just committed the markup builders feature. The documentation is supposed to be better that that but it not even worse, it is blatantly misleading.

I just fixed a 6-year old bug in the 5 lines of code that I use at least 100 times a day, every day, including weekends and holidays. Now, I can finally publish it.

function truncate_pwd
{
 if [ $HOME == $PWD ]
 then
   newPWD="~"
 elif [ $HOME ==  ${PWD:0:${#HOME}} ]
 then
   newPWD="~${PWD:${#HOME}}"
 else
   newPWD=$PWD
 fi

  local pwdmaxlen=15
  if [ ${#newPWD} -gt $pwdmaxlen ]
  then
    local pwdoffset=$(( ${#newPWD} - $pwdmaxlen  ))
    newPWD=".+${newPWD:$pwdoffset:$pwdmaxlen}"
  fi
}

PROMPT_COMMAND=truncate_pwd
PS1="${ttyname}@\[${HOST_COLOUR}\]\h\[${RESET_COLOR}\]:\${newPWD}\\$ "

Just put the above snippet of code into ~/.bashrc

Debian shows the absolute path in the command prompt by default, and it can be really long, sometimes.To fix this, we can limit the command prompt to show only the last x characters using only the variable expansion features of bash 2.0.5+. Since this code does not fork out sed, tr or wc, it is blazingly fast.