Rails - Feb 2007 - Lifespan of a Controller instance variable

If I drop an instance variable into my controller, how long does it
survive?

For example,

class FooController < ApplicationController

  def foo
    @foo ||= some_calculated_value
  end

  def some_calculated_value
    # code goes here...
  end

end

So, how long does @foo survive?  For the duration of one request?  Or
something else?

Many thanks.

-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

On Feb 2, 4:24 pm, Robert Head
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> If I drop an instance variable into my controller, how long does it
> survive?
>
> For example,
>
> class FooController < ApplicationController
>
>   def foo
>     @foo ||= some_calculated_value
>   end
>
>   def some_calculated_value
>     # code goes here...
>   end
>
> end
>
> So, how long does @foo survive?  For the duration of one request?  Or
> something else?
>
> Many thanks.
>
> --
> Posted viahttp://www.ruby-forum.com/.
Just one request unless you stuff it in the session hash.
If the method you use to set it is a before_filter, then it will be
available to everything further down the chain, but only for that one
request.

_Kevin


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Hi Robert,

Robert Head wrote:
> If I drop an instance variable into my controller,
> how long does it survive?
>
> For example,
> So, how long does @foo survive?  For the
> duration of one request?  Or something else?
In general, instance variables live for one request/response cycle.  It can 
be shorter than that though if, for example, you do a redirect to another 
controller.

hth,
Bill 



--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Excellent.  Confirms my observations.

Follow up question...

Don''t Controller instance variables get shared in weird ways with
helpers and views?  Can someone describe exactly where they are
available and where they are not?  Same with Helper instance variables.

Thanks again,
Rob

-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

I believe all controller instance variables are made available to
views and helpers. A good rule of thumb is only set instance variables
for things you really need to get access to in the view, otherwise
just us a local/temp. Furthermore, if there are instance variables
that you access throughout your app (that are set in
ApplicationController for instance), add some accessor methods to
encapsulate them (in the same way that session and params encapsulate
the data).

On Feb 2, 11:19 pm, Robert Head
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> Excellent.  Confirms my observations.
>
> Follow up question...
>
> Don''t Controller instance variables get shared in weird ways with
> helpers and views?  Can someone describe exactly where they are
> available and where they are not?  Same with Helper instance variables.
>
> Thanks again,
> Rob
>
> --
> Posted viahttp://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Bill Walton wrote:
> Hi Robert,
> 
> Robert Head wrote:
> 
>> If I drop an instance variable into my controller,
>> how long does it survive?
>>
>> For example,
> 
>> So, how long does @foo survive?  For the
>> duration of one request?  Or something else?
> 
> In general, instance variables live for one request/response cycle.  It can
> be shorter than that though if, for example, you do a redirect to another 
> controller.
Don''t mean to be boor, but a redirect *is* a response... it''s
the "yeah,
I got yer post, now here''s where to go for the next page"
response.

So, I''d say that instance variables live for one request/response 
cycle... period.

b

> 
> hth,
> Bill 
> 
> 
> 
> > 
> 
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Hi Ben,

Ben Munat wrote:
> Don''t mean to be boor, but a redirect
> *is* a response... it''s the "yeah, I got
> yer post, now here''s where to go for
> the next page" response.
Thanks for posting this.  I''d never really grokked the fundamentals of
why
the instance variables didn''t live through a redirect.  The mental
model I
had was that the cycle ended with a render and that server-side processing 
that included a redirect was occurring as one ''unit''. 
I''d put the life-span
question in the "That''s just how it works.  Here''s how to
deal with it."
pile.  Your post caused me to reread the doc on redirect and there it was in 
black and white.  Duh ;-)  Makes total sense now.  Pulls a couple of loose 
threads re: Rails architecture together for me.  Thanks again.

Best regards,
Bill 



--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---