From: "David A. Black" <dblack@...>
Date: 2009-09-22T21:52:49+09:00
Subject: Re: Accessing an instance variable in another method

Hi --

On Tue, 22 Sep 2009, Subashini Kumar wrote:

> Hi,
> I am new to Rails.I tried developing a basic quiz application.Please
> help me out in my doubt.Thanks in advance
>
> <% CODE %>
>
> class QuizController < ApplicationController
>
>  def index
> # i have retrieved the first five questions from the database for
> displaying the #question to user
>    @quiz=Quiz.find(:all,:limit=>5)
>
>  end
>
>  def report
>
>  end
>
> # this method checks the answer and gives score
>  def checkanswer
> # here i want to access the @quiz object which is a set of questions i
> have #retreived from the database.Hot to access it?
>  end
>
>  end

There are two things you have to keep in mind here. The first is that
every instance of a class has its own supply of instance variables:

   class Person
     def initialize(name)
       @name = name
     end

     def print_name
       puts @name
     end
   end

   a = Person.new("David")
   a.print_name              # David
   b = Person.new("Joe")
   b.print_name              # Joe

So every time I create a new Person object, that object has a fresh
"slate" of instance variables.

The second thing you need to know is that in your Rails application,
every request creates a new controller object. So the @quiz variable
you create for the index request is not going to exist on the next
request (i.e., when the person looking at the index clicks on a link
and your application goes through another request/response cycle).
Instance variables are "sticky", but only for the lifetime of the
object.


David

-- 
David A. Black, Director
Ruby Power and Light, LLC (http://www.rubypal.com)
Ruby/Rails training, consulting, mentoring, code review
Book: The Well-Grounded Rubyist (http://www.manning.com/black2)