Rails - Aug 2006 - Instance variables best solution for wizard type

Hello All,

This is my first post so if you could not crucify me publicly I would
appreciate.

I beleive I have a simple question but do not manage to find the answer.

Basically I want to create a wizard type of system where the customer
enters some info on the first page then goes to step 2, some more
info, then step 3 and finishes. Each steps represent an action in the
same controller. I have declared an instance variable (@step1) in the
first step and needs it in the last finishing step.

If I try to use that variable, it gives me a null pointer exception.
The lifespan of a instance variable is between the controller and the
view and dies thereafter? Can it be for the entire lifespan of the
controller?

More concrete exemple:

--- step 1 ---
name , address ect... + internal info set within the action
--- step 2 ---
depends on info entered in step 1 +
favorite cat
-- step 3 ---
depends on step2 + favorite dog
-- step 4 --
finishes -> saves into the db === > name, address, internal info set
by action "step1" + favorite cat + favorite dog

How can in action "step4" access the data set internaly un
"step1"
plus the data entered by the client in the further 3 actions?

Hope it is clear engough. I heard of acts_as_wizard but beleive this
situation do not require a plugin - good for my learning curve as
well...

Cherio,
Carl

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Hello Again,

Should I use accessors by any chance? Any exemple would be much appreciated.

Carl

On 8/29/06, Carl-Gustaf Harroch
<charroch-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Hello All,
>
> This is my first post so if you could not crucify me publicly I would
> appreciate.
>
> I beleive I have a simple question but do not manage to find the answer.
>
> Basically I want to create a wizard type of system where the customer
> enters some info on the first page then goes to step 2, some more
> info, then step 3 and finishes. Each steps represent an action in the
> same controller. I have declared an instance variable (@step1) in the
> first step and needs it in the last finishing step.
>
> If I try to use that variable, it gives me a null pointer exception.
> The lifespan of a instance variable is between the controller and the
> view and dies thereafter? Can it be for the entire lifespan of the
> controller?
>
> More concrete exemple:
>
> --- step 1 ---
> name , address ect... + internal info set within the action
> --- step 2 ---
> depends on info entered in step 1 +
> favorite cat
> -- step 3 ---
> depends on step2 + favorite dog
> -- step 4 --
> finishes -> saves into the db === > name, address, internal info set
> by action "step1" + favorite cat + favorite dog
>
> How can in action "step4" access the data set internaly un
"step1"
> plus the data entered by the client in the further 3 actions?
>
> Hope it is clear engough. I heard of acts_as_wizard but beleive this
> situation do not require a plugin - good for my learning curve as
> well...
>
> Cherio,
> Carl
>

-- 
Carl-Gustaf Harroch

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Hi --

On Tue, 29 Aug 2006, Carl-Gustaf Harroch wrote:
>
> Hello All,
>
> This is my first post so if you could not crucify me publicly I would
> appreciate.
>
> I beleive I have a simple question but do not manage to find the answer.
>
> Basically I want to create a wizard type of system where the customer
> enters some info on the first page then goes to step 2, some more
> info, then step 3 and finishes. Each steps represent an action in the
> same controller. I have declared an instance variable (@step1) in the
> first step and needs it in the last finishing step.
>
> If I try to use that variable, it gives me a null pointer exception.
> The lifespan of a instance variable is between the controller and the
> view and dies thereafter? Can it be for the entire lifespan of the
> controller?
It is :-)  The thing is, though, the lifespan of the controller is
only one action.

The controller is actually an instance of your controller class.  When
you run an action -- say, ''login'' for a user controller --
what
happens is (in simplified form):

   c = UserController.new # create an instance of the controller
   c.login                # call a method ("action") on that instance

On the next action, a new instance of your controller is created.  And
so on.

Every object has its own instance variables; therefore, each
controller instance has its own instance variables.

Have you looked at the special ''session'' hash?  You can use it
to
store data between actions.


David

-- 
                   David A. Black |
dblack-TKXtfPMJ4Ozk1uMJSBkQmQ@public.gmane.org
Author of "Ruby for Rails"   [1] | Ruby/Rails training &
consultancy [3]
DABlog (DAB''s Weblog)        [2] | Co-director, Ruby Central, Inc.  
[4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org

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Carl-Gustaf Harroch wrote:
> If I try to use that variable, it gives me a null pointer exception.
> The lifespan of a instance variable is between the controller and the
> view and dies thereafter? Can it be for the entire lifespan of the
> controller?
Hi Carl,

A new instance of the controller is creates for each request, so 
variables do not persist.  The best way would be to store the info you 
have so far in a DB record.

Ideally an extra column or somesuch to indicate what ''page''
you are up
to for that record, and simply update the record as you go.

The share-nothing approach lets Rails apps scale easily by adding other 
appservers etc.

Alan

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

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Carl-Gustaf Harroch wrote:
> Hello All,
> 
> This is my first post so if you could not crucify me publicly I would
> appreciate.
> 
> I beleive I have a simple question but do not manage to find the answer.
> 
> Basically I want to create a wizard type of system where the customer
> enters some info on the first page then goes to step 2, some more
> info, then step 3 and finishes. Each steps represent an action in the
> same controller. I have declared an instance variable (@step1) in the
> first step and needs it in the last finishing step.
> 
> If I try to use that variable, it gives me a null pointer exception.
> The lifespan of a instance variable is between the controller and the
> view and dies thereafter? Can it be for the entire lifespan of the
> controller?
The internet is "stateless". If you want to reuse data between
actions,
or page requests, you have to save it in a session or cookie or the 
database.

def step1
  session[:step1] = params[:step1]
end

def step2
  @step1 = session[:step1]
end

or something to that effect

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

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