square brackets [] class method of Hash

[] class method of Hash converts an array into a hash.

irb(main):001:0> Hash["name","subbu","profession","programmer"]
=> {"name"=>"subbu", "profession"=>"programmer"}
irb(main):002:0> my_array = %w{ a b c d }
=> ["a", "b", "c", "d"]
irb(main):003:0> Hash[*my_array]
=> {"a"=>"b", "c"=>"d"}

Preventing sensitive data from being logged in Rails log file

filter_parameter_logging :password

References:
1. http://api.rubyonrails.org/classes/ActionController/Base.html#M000441
2. Page 610 of 'Agile Web Development with Rails'

Route Globbing

The default route "map.connect ':controller/:action/:id'" is sufficient in most of the cases when dealing with URLs and routing. It matches most of the common URLs that are coming your way. But what if we need an URL like:

www.mysite.com/2008/02/5/28/18/30/20 which might mean:
www.mysite.com/year/month/week/day/hour/minute/second

There is something called as Route Globbing to solve this problem. In your routes.rb file specify the following line:

map.connect 'year/month/*values'

Routing engine bundles all the values after the third slash into params[:values] as an array. So your year/month action will have access to this array. The params[:value] will now look like ["5","28","18","30","20"].

If we want another controller to receive the URL, then we can say:

map.connect 'year/month/*values', :controller => "accounts"

Route globbing could be helpful if we are allowing users to enter some kind of organizational structure or file paths in to the URL.

String: extract a single character

Whenever I wanted to extract a single character from a string, invariably I started with something like "hello"[1] and Ruby returns 104. That's the ascii code for 'h'. Its not at all useful. I should practice saying "hello"[0,1] which will return what I want, i.e. 'h'.

require and load won't reload the file with reload! in rails console

I have the statement "require 'primary_user' " in one of my models of my Rails application. Usually whenever I do a 'reload!' in my rails console, it reloads all the models and their associates files so that any changes to code can be seen in the console. But there is a catch to that reload!. It doesn't reload any of the files loaded using the 'require' statement. So my 'primary_user' file wasn't getting reloaded. Strange. But that's how it works. I tried changing 'require' to 'load' but no use.

Rails without a database

Add this to environment.rb:

config.frameworks -= [ :active_record]

This is what lines 19 to 21 in environment.rb say (Rails version 2.0.2):

  # Skip frameworks you're not going to use (only works if using vendor/rails).
  # To use Rails without a database, you must remove the Active Record framework
  # config.frameworks -= [ :active_record, :active_resource, :action_mailer ]

eval

eval("foo", binding)
Evaluate string in the context of binding. In this case 'foo' is executed as code in the context of binding. The second parameter is optional. It could either be a proc object or a binding object. If the second parameter is missing then the scope is set to current.

class_eval
Evaluate the code inside the context of a class. Example:

Array.class_eval <<-addons
  def total
    self.inject do |s,e|
      s+e
    end
  end
addons

a=[1,2,3,4]
puts a.total

We can say something like "Array.class_eval('some goes here')" and the code will be executed within the context of Array class.

module_eval
Same as class_eval

Here is an excellent article:
http://www.infoq.com/articles/eval-options-in-ruby