Difference between "and" and "&&"

klasses = ['last'] && txt = '' if idx == (tabs.length - 1)

At the end of this statement klasses will contain "".

klasses = ['last'] and txt = '' if idx == (tabs.length - 1)

At the end of this statement klasses will contain ['last'] which was what I intended. But the first statement wasn't returning that.

A good explanation is here http://stackoverflow.com/questions/1426826/difference-between-and-and-in-ruby

Missing gems even though they are present

Have you seen the following only to realize all those are already installed?

Missing these required gems:
  rspec  = 1.3.0
  rspec-rails  = 1.3.2

My environment.rb has entries for both of them like:

config.gem 'rspec', :version => '1.3.0'
config.gem 'rspec-rails', :version => '1.3.2'

After a lot of hair pulling I found we need to add another argument to that config.gem. The following fixed the problem:

config.gem 'rspec', :version => '1.3.0', :lib => false
config.gem 'rspec-rails', :version => '1.3.2', :lib => false

Export MySQL query result to a CSV file

SELECT a,b,a+b INTO OUTFILE '/tmp/result.txt'
  FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
  LINES TERMINATED BY '\n'
  FROM test_table;

http://tlug.dnho.net/node/209
http://dev.mysql.com/doc/refman/4.1/en/select.html

Another example:

SELECT v.id,v.name,t.name,d.name INTO OUTFILE '/root/tr_villages.csv' 
  FIELDS TERMINATED BY ',' 
  OPTIONALLY ENCLOSED BY '"' 
  LINES TERMINATED BY '\n' 
  FROM villages v JOIN taluqs t ON v.taluq_id=t.id JOIN districts d ON t.district_id=d.id 
  WHERE t.district_id IN (163,164,165,166);

IRB tricks: assign last statement's return value to a var

irb(main):001:0> 1+2
=> 3
irb(main):002:0> a=_
=> 3
irb(main):003:0> a
=> 3

Underscore assigns the last executed statement's return value to a.

Anonymous functions

An interesting fact:

var sum = function(x,y,z) {
 return (x+y+z);
}(1,2,3);

is an anonymous function. That means sub is now 6. If you call sum with any arguments it will bark at you. Where as this:

var sum = function(x,y,z) {
 return (x+y+z);
};

is a named function. Sum is a function that accepts 3 arguments. If you call sub(2,3,5), it will return 10.

Errno::ECONNREFUSED: Connection refused - connect(2)

Errno::ECONNREFUSED: Connection refused - connect(2)

If you get this error, one of the reason could be incorrect or no ActionMailer settings. The following structure needs to be present in your production.rb (or whatever config file):

ActionMailer::Base.smtp_settings = {
:address => 'smtp.gmail.com',
:port => 587,
:domain => 'mydomain.com',
:authentication => :plain,
:user_name => 'user@mydomain.com',
:password => 'password'
}

Using define_method to create a method that takes arguments

http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/211436
http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/211440

Example:

Setting.all.each do |setting|
define_method setting.name do |*a|
  r = find(:first, :include => :setting, :conditions => ["setting_id = ?", setting.id])
  full_record = (a.length == 0) ? false : a[0]
  full_record ? r : r.value
end
end