Session Issue in rails?

Question

Suppose this is my users controller:-

class UsersController < ApplicationController
 def show
  @user = session[:user]
 end

 def prepare
  session[:user]= User.find(:first)
  redirect_to :action => 'show'
end

def update
 @user = session[:user]
 @user.name = 'rai'
redirect_to :action => 'show'
end
end

View for show.html.erb

<%= @user.name %>
Show page
<%= link_to 'Update', :action=> 'update' %>

Now Explaining the issue:--- Suppose first time user opens the browser with

 http://localhost:3000/users/prepare

o/p will be:---

 Mohit Show page Update  // supposing user table has values mohit as name

Now when he click on update he will get as output like this:--

  rai Show page Update

But this should not happen cause

firstly when are at prepare action where value is fecthced from db and its mohit. and then he is redirected to show ie displying the values from session. ie mohit

Now when user click on the update he is redirected to update when value from session is stored to a user instance and the name attribute of that user instance has been modified to rai. and finally redirected to show page.

Now in this page when user's name is displayed its showing rai.. thats the QUESTION why?? cause session should store the same mohit value cause we havnt made any change in session..

Answer 1

When you are doing

@user = session[:user]

@user variabe is assigned reference to the object session[:user], not the copy of it. So when you are modifying @user, session[:user] is also modified, as they are essentially the same object.

Answer 2

I'm not sure, but I think it is something with hashes and classes and about copying them. So when you do:

@user = session[:user]

You are not making a copy of object but it is something likre reference in C++, both @user and session[:user] are reffering to the same object, so when you modify one, you get both modified.

Example from console:

a = {}
a[:user] = User.first
a[:user].firstname           # => "Mohit"
b = a[:user]
b.firstname = 'rai'
a[:user].firstname           # => 'rai'
a[:user] = User.first
a[:user].firstname           # => 'Mohit'