Forum: Ruby on Rails controller instance variables

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60a69053360ce8ae82d5968b228856ee?d=identicon&s=25 Peter Ab (alderion)
on 2008-10-04 17:36
hi, i'm very new to ruby and rails so be gentle.  i am trying to set up
a form that uses some validation but i'm having issues.  i have a
controller class that contains 2 methods: one for showing the form and
another for processing the form.  like so:

def show_form
  store = Store.find_by_id(session[:store_id])
  @all_balls = store.balls
  @ball_sizes = store.ball_sizes
end

def complete_form
  @picked_ball = session[:picked_ball]
  if check_nil @picked_bread, 'Please choose a ball.'
      return
  end

  @picked_ball_size = session[:picked_ball_size]
  if check_nil @picked_ball_size, 'Please choose a ball size.'
      return
  end

  # save stuff off into db
end

def check_nil(var_to_check, message)
  if var_to_check.nil?
    flash[:notice] = message
    redirect_to :back
    return true
  end
  false
end

my problem is that if the user selects a ball but forgets to select a
ball size, i go back to the form but it seems that i've lost all memory
of @picked_ball.  i don't want to user to have to select the ball again.
i want it to be selected when the page is redisplayed with the error.
do i have to put this stuff in the session?  i hope i don't because
there are actually a lot more items on the page, i've cut it down so my
post isn't quite as long.

also, here is my form:

<% form_tag(:action => 'complete_form') do %>

  <h3>balls</h3>
  <% for ball in @all_balls %>
    <%= radio_button_tag 'picked_ball', ball.name, @picked_ball ==
ball.name %> <%= ball.name %><br />
  <% end %>

  <% for size in @all_sizes %>
    <%= radio_button_tag 'picked_size', size.name, @picked_size ==
size.name %> <%= size.name %><br />
  <% end %>

<% end %>

thanks for any and all help.

-peter
81b61875e41eaa58887543635d556fca?d=identicon&s=25 Frederick Cheung (Guest)
on 2008-10-04 17:57
(Received via mailing list)
On Oct 4, 4:36 pm, Peter Ab <rails-mailing-l...@andreas-s.net> wrote:
> my problem is that if the user selects a ball but forgets to select a
> ball size, i go back to the form but it seems that i've lost all memory
> of @picked_ball.  i don't want to user to have to select the ball again.
> i want it to be selected when the page is redisplayed with the error.
> do i have to put this stuff in the session?  i hope i don't because
> there are actually a lot more items on the page, i've cut it down so my
> post isn't quite as long.
>
Typically one deals with this by re-rendering the form, not by
redirecting. You'll very often see this pattern:

@foo = Foo.new params[:foo]
if @foo.save
  #success
  redirect_to ...
else
  render :action => 'new'
end

Fred
60a69053360ce8ae82d5968b228856ee?d=identicon&s=25 Peter Ab (alderion)
on 2008-10-04 18:20
Frederick Cheung wrote:
> Typically one deals with this by re-rendering the form, not by
> redirecting. You'll very often see this pattern:
>
> @foo = Foo.new params[:foo]
> if @foo.save
>   #success
>   redirect_to ...
> else
>   render :action => 'new'
> end

thanks for the help, fred.  i'm still a little confused.  it is my
understanding that "actions" are methods in the controller.  would that
code you posted be in a new def?  i.e.

def new
  # code you posted
end

are you saying i need to have the show and the handle performed by the
same method?  that doesn't make sense to me as in the 'show' case, i'm
not looking for anything but in the 'complete' case, i am.  how do i
know what i need to do if i have only one method doing both?

is there some tutorial somewhere you could point me to that goes in
depth on forms and best practices in using them?  a tutorial that goes
into one controller method v. two; model object forms v. forms with just
fields on them, etc.

thanks,

-peter
60a69053360ce8ae82d5968b228856ee?d=identicon&s=25 Peter Ab (alderion)
on 2008-10-04 19:31
ok, i think i understand now after playing with it for a bit.  it looks
like the 'render :action => new' runs the code from the new method but
with all the context of the method from which it came where as
redirect_to starts with a clean context.

so, i still have 2 actions (methods) show and complete but if i find an
error in complete, i now *render* show again and have all the context of
what i had in complete.  when i used redirect_to, it also went to show
but it cleared out the context.

thanks for the pointer, fred.

-peter
81b61875e41eaa58887543635d556fca?d=identicon&s=25 Frederick Cheung (Guest)
on 2008-10-04 19:46
(Received via mailing list)
On 4 Oct 2008, at 18:31, Peter Ab wrote:

>
>
> ok, i think i understand now after playing with it for a bit.  it
> looks
> like the 'render :action => new' runs the code from the new method but
> with all the context of the method from which it came where as
> redirect_to starts with a clean context.

It does not run the new method at all. It just renders the template
that the new action would have rendered.
So in a typical example, the new method would just do

def new
   @foo = Foo.new
end
ie the new method just starts out with an empty (all attributes set to
the defaults) instance of Foo.

If you call render from your create method then instead of having that
empty instance of Foo, you've got the one you created from the user
input so all the fields the user had filled it would be filled in and
so on.

> so, i still have 2 actions (methods) show and complete but if i find
> an
> error in complete, i now *render* show again and have all the
> context of
> what i had in complete.  when i used redirect_to, it also went to show
> but it cleared out the context.

That's about right.

Fred
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