Date Calculation in Rails

>> Date.new( 2008, 1, 1 ).to_time.advance( :months => 1 )
=> Fri Feb 01 00:00:00 +0000 2008

>> Date.new( 2008, 2, 1 ).to_time.advance( :months => 1 )
=> Sat Mar 01 00:00:00 +0000 2008

>> Date.new( 2008, 1, 1 ).to_time + 1.month
=> Thu Jan 31 00:00:00 +0000 2008

Extracted from here:

http://roninonrails.blogspot.com/2008/01/beware-of-rails-date-arithmetic.html

Get Month Name in Rails

To get month name as constants, do the following

require 'date'

for i in (1..12)

@month = Date::MONTHNAMES[i]

end

Date Format in strftime

Format	Meaning
%a	The abbreviated weekday name (“Sun'’)
%A	The full weekday name (“Sunday'’)
%b	The abbreviated month name (“Jan'’)
%B	The full month name (“January'’)
%c	The preferred local date and time representation
%d	Day of the month (01..31)
%H	Hour of the day, 24-hour clock (00..23)
%I	Hour of the day, 12-hour clock (01..12)
%j	Day of the year (001..366)
%m	Month of the year (01..12)
%M	Minute of the hour (00..59)
%p	Meridian indicator (“AM'’ or “PM'’)
%S	Second of the minute (00..60)
%U	Week number of the current year, starting with the first Sunday as the first day of the first week (00..53)
%W	Week number of the current year, starting with the first Monday as the first day of the first week (00..53)
%w	Day of the week (Sunday is 0, 0..6)
%x	Preferred representation for the date alone, no time
%X	Preferred representation for the time alone, no date
%y	Year without a century (00..99)
%Y	Year with century
%Z	Time zone name
%%	Literal “%'’ character

Attachment_fu Installation

Installing Attachment_fu plugin steps as follows:

1. Install Freeimage plugin for image processing:

sudo port selfupdate

sudo port install freeimage (link)

MacPorts installation notes can be obtained from here.

2. Install ImageScience

sudo gem install -y image_science

3. Install Attachment_fu

script/plugin install http://svn.techno-weenie.net/projects/plugins/attachment_fu/

Mongrel_rails

To use mongrel_rails in production, you need to create a service to run in your Windows Server.

Navigate to the directory where rails app are located.

Replace (service name) including bracket with your service name .

Here is the command:

Install service:

mongrel_rails service::install -N (service name) -e (environment. e.g. production) -p (port to be used)

Remove the service:

mongrel_rails service::remove -N (service name)

That's all. Then you can configure lightttpd to point to the mongrel web app.

To start the service from command line:

net start (service name)

Uninstall SleepWatcher

To unistall SleepWatcher (an useful tool for sleep/wake in OSX)

uninstalling sleepwatcher:

go to terminal
sudo rm /usr/local/sbin/sleepwatcher
sudo rm /usr/local/share/man/man8/sleepwatcher.8
sudo rm /etc/rc.sleep
sudo rm /etc/rc.wakeup

go to finder delete: /Library/StartupItems/SleepWatcher

need your passwd

SQL SUM() in Rails

In Rails, Active Record support many types of calculations. It saves us from executing SELECT SUM(x) using the query. Everything can be shorten down one line of code.

Example:

To find sum of all items in a location:

Item.sum('location_id', :conditions =>['location_id = ?', location.id])

Similar to avg and others. See ActiveRecord API for more info.