Large development@Rails

With my recent Googling, I could crawl through few sites, blogs and data analytic graphs. I was shocked to know the jumping intercourse relation of web development with RoR, Specially on the blog http://www.railsonwave.com/ about the migration of site http://www.yellowpages.com/ from JAVA to Rails with so many positive results. I won’t make you to go through the blog and read each and every line unless you want…

Yes I am up with few highlights :

· Yellowpage has got 23 million visitors a month, this shows the Rails is fit for a large application in terms of performance.

· From 125.000 lines of code in Java, mainly written by external consultants from 2004 to 2005, to at least 20.000 lines of code in only 3 months of development from a team of 4 developers.

Sites those are developed in Rails and could be matter of a crown here, I would love to list few of them: (Yeah all of them has got 10+ million visitors@per month)

· http://www.yellowpages.com/

· http://www.revolutionhealth.com/

· http://www.43things.com/

· http://odeo.com/

· http://twitter.com/

Few more can be highlighted here:

· http://www.spock.com/

· http://penny-arcade.com/

· http://chowhound.com/

Generate Unique ID

Here is a very simple way to generate a unique id.
[Background support : Abhishek S.]

def generate_unique_id( len )
    chars_pattern = ("a".."z").to_a + ("A".."Z").to_a + ("0".."9").to_a
    unique_id = ""
    1.upto(len) {
			|i| unique_id << chars_pattern[rand(chars_pattern.size-1)]  }
    return unique_id
end
#generates a key of length 10
mykey = generate_unique_id(10)
print mykey # gives a result like "qeKX0myIQh"

render in rails

What do you see in a browser is nothing but a response; which is a combination of header and some document data.

From where does it come? -> Through the action of some controller.

Each action results in a response,

response = headers + document content

This resonse object is generated using various types of renders/redirects. Action Controller sends content to the user by using these rendering methods.

By default, actions are rendered within the current layout (if one exists)

• AUTOMATIC RENDER

def myname
@name = “rajesh”
end

myname.rhtml ->My name is “#{@name}”

Yes this is also a type of render; an automatic rendering using instance var.

• SIMPLE RENDER

def method1
@val = 30
render :action => “method2″, :layout => “mylayout1″
return
end

> This will execute the view of method2,

> Nothing will appear as a view for method1

> there is no relation what all defined in action def method2

> Any instance var defined before this statment can be executed in the view for method2 (not in action)
means in readered view of method2.rhtml
puts @val # returns you 30
where as
def method2
puts @val # dont expecct 30 in direct way
end
> TWO render is not possible in same action, else gives error, coz control exececutes code after the render statement.

• RENDER PARTIAL

def method1
@val = 30
render :partial => “my_first_partial”
return
end

> render partial can be used in both controller as well as view, while plain render can be used in controller only
> In controller if you are using -> render :partial => “my_first_partial”
Layout will be lost of the current method i.e method1; But if you want to preserve it use layout as true
render :partial => “my_first_partial”, :layout => ‘true’
> If you are using it in view then layout of method1 will be preserved.

> instance var is well accessible in partial file, but if you want to pass the local var, then must use locals
render :partial => “my_first_partial” , :locals => {:q => 90}

• RENDERING TEXT

render :text => “hello”, :layout => true
render :inline => “<%= ‘hello, ‘ * 3 + ‘again’ %>”, :layout => true

• REDIRECTS_TO

redirect_to refers the method while render seeks you to the corresponding view.
You cant have these two together without any conditional statment.

RENDER -> populates a VIEW

REDIRECT -> hammers an ACTION

[Background support : Himanshu P.]

Overriding Active Record

1. If one wishes the table name should be singular instead of plural
Set the below configuration

ActiveRecord::Base.pluralize_table_names = false

2. If you want your model’s classname should represent a table of someother name

class Name < ActiveRecord::Base
   # by defualt it refers to "names" table in DB
   # Now let it refer to "nicknames"
   set_table_name "nickname"
end

3. If your primary key column is not named simply “id”, you can override this from within the class definition as well:

class Name < ActiveRecord::Base
     set_primary_key "nameid"
end

so when you want to save a record in DB (you must still use the id attribute to do so)

name_obj = Name.new
name_obj.id = 'N999'   #use the same   format this is eqivaled in saying name_obj.nameid='N999'
name_obj.save

but while accessing such record

print name_obj.nameid  # gives a result of "N999"

RailsConf 2008

May 29-June 1, 2008
Portland, Oregon

RailsConf is the official event for the growing Rails community.

Exception Handling in Ruby

>begin expression executes its body and returns the value of the last evaluated expression.
>Any error in begin part will be caught by rescue depending upon parameters
>ensure is the one which must be exectued irrespective of exception occured or not
>An error message caught by an exception can be accessed using $!

For Java Programmers [ begin => try ; rescue => catch; ensure => finally]

begin
 p "I am doing well"
 p "so well .. and well"
 a = 8/0
rescue
 p "Something went wrong => " + $!
ensure
 p "Oh Somehow I could finish my work"
end

O/P:

“I am doing well”
“so well .. and well”
“Something went wrong => divided by 0″
“Oh Somehow I could finish my work”

a = 8
b = 0
begin
 p "I am doing well"
 p "so well .. and well"
 if a==18
    p "I am happy with a as 8"
 elsif b == 0
    p "Lets say I dont want this"
    raise Exception
 else
    raise
 end

rescue
    p "Exception 1 caught here " + $!
rescue Exception
    p "Exception 2 caught here " +$!
ensure
 p "Oh Somehow I could finish my work"
end

O/P for [[ a = 8 and b = 0 ]]
“I am doing well”
“so well .. and well”
“Lets say I dont want this”
“Exception 2 caught here Exception”
“Oh Somehow I could finish my work”

O/P for [[ a = 8 and b = 1 ]]
“I am doing well”
“so well .. and well”
“Exception 1 caught here “
“Oh Somehow I could finish my work”