Rails - Jan 2006 - Can only render or redirect once per action - why?

I ran into this error message a quite a few times since my app requires
branching to different pages from the same action... say using a switch
statement. Ofcourse I found that you can use  multiple redirects or renders
if you do

render :action => ''new'' and return false

I hate to code something I don''t understand fully. Any explanation of
this
will be greatly appreciated!

Thanks,

bakki kudva
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How would one send output to the browser twice? (minus ajax usuage of
course) Thats really the simple reasoning behind it. The render tells
rails what to send back to the browser and hence, only has one shot at
it*.

If you need to render another view from your current action, here''s
the common approach:

def first_action
  if some_condition
     render :action => :second_action #renders the second action_view
but doesn''t actually call the second_action method
  end
  #otherwise it will just render the first_action view
end

def second_action
    if something
        redirect_to :action => "first_action"
    else
        render :layout => false #just an example of rendering with no layout
    end
end

Hope this helps some.
-Nick

On 1/10/06, Bakki Kudva <bakki.kudva@gmail.com>
wrote:
> I ran into this error message a quite a few times since my app requires
> branching to different pages from the same action... say using a switch
> statement. Ofcourse I found that you can use  multiple redirects or renders
> if you do
>
>  render :action => ''new'' and return false
>
>  I hate to code something I don''t understand fully. Any
explanation of this
> will be greatly appreciated!
>
>  Thanks,
>
>  bakki kudva
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>

Nick,

Thanks for the quick repy. I realize you wouldn''t send output to the
browser
twice. For example in the following code...

  def create
    @user = User.new(params[:user])
    @confirm = params[:confirm]
    unless @user.password == @confirm
      flash[:notice] = ''Password mismatch. Please type them
again.''
      render :action => ''new'' and return false
    end
    if @user.save
      flash[:notice] = ''Student was successfully created.''
      redirect_to :action => ''list''
    else
      render :action => ''new''
    end
  end

I get the error because of the render statement within the unless --- end
block. I had assumed that a render statement terminates the action. But it
apparently does not unless you explicitly tell it to with the return
statement. I wonder if there is any reason for this. Doesn''t a render
sort
of imply that you are done with the action, just like the redirect_to and
any statements following it wouldn''t be reached?

bakki

On 1/10/06, Nick Stuart <nicholas.stuart@gmail.com>
wrote:
>
> How would one send output to the browser twice? (minus ajax usuage of
> course) Thats really the simple reasoning behind it. The render tells
> rails what to send back to the browser and hence, only has one shot at
> it*.
>
> If you need to render another view from your current action,
here''s
> the common approach:
>
> def first_action
>   if some_condition
>      render :action => :second_action #renders the second action_view
> but doesn''t actually call the second_action method
>   end
>   #otherwise it will just render the first_action view
> end
>
> def second_action
>     if something
>         redirect_to :action => "first_action"
>     else
>         render :layout => false #just an example of rendering with no
> layout
>     end
> end
>
> Hope this helps some.
> -Nick
>
> _______________________________________________
>
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I think it is for the case where you want to redirect a user because 
he/she is not authorized:

unless user.authorized?
 redirect_to ...
end

render ...

The render call would be executed and if the user blocked the redirect 
he/she would be able to see the page.

And validations should be in your model anyway. There is 
validates_confirmation_of for this password-confirmation ;-)

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

On 1/10/06, Bakki Kudva <bakki.kudva@gmail.com>
wrote:
> Nick,
>
>  Thanks for the quick repy. I realize you wouldn''t send output to
the
> browser twice. For example in the following code...
>
>    def create
>      @user = User.new(params[:user])
>      @confirm = params[:confirm]
>      unless @user.password == @confirm
>        flash[:notice] = ''Password mismatch. Please type them
again.''
>        render :action => ''new'' and return false
>      end
>      if @user.save
>        flash[:notice] = ''Student was successfully
created.''
>        redirect_to :action => ''list''
>      else
>        render :action => ''new''
>      end
>    end
>
>  I get the error because of the render statement within the unless --- end
> block. I had assumed that a render statement terminates the action. But it
> apparently does not unless you explicitly tell it to with the return
> statement. I wonder if there is any reason for this. Doesn''t a
render sort
> of imply that you are done with the action, just like the redirect_to and
> any statements following it wouldn''t be reached?
>
>  bakki
>
> On 1/10/06, Nick Stuart <nicholas.stuart@gmail.com> wrote:
> > How would one send output to the browser twice? (minus ajax usuage of
> > course) Thats really the simple reasoning behind it. The render tells
> > rails what to send back to the browser and hence, only has one shot at
> > it*.
> >
> > If you need to render another view from your current action,
here''s
> > the common approach:
> >
> > def first_action
> >   if some_condition
> >      render :action => :second_action #renders the second
action_view
> > but doesn''t actually call the second_action method
> >   end
> >   #otherwise it will just render the first_action view
> > end
> >
> > def second_action
> >     if something
> >         redirect_to :action => "first_action"
> >     else
> >         render :layout => false #just an example of rendering with
no
> layout
> >     end
> > end
> >
> > Hope this helps some.
> > -Nick
> >
> > _______________________________________________
> >
>
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>
Render doesn''t return, for reverse-compatibility reasons.

--
Kyle Maxwell
Chief Technologist
E Factor Media // FN Interactive
kyle@efactormedia.com
1-866-263-3261

Good point Jules, Thanks for pointing that out. I am still cutting my teeth
on this :)

-bakki

On 1/10/06, Jules Jacobs <julesjacobs@gmail.com>
wrote:
>
> I think it is for the case where you want to redirect a user because
> he/she is not authorized:
>
> unless user.authorized?
> redirect_to ...
> end
>
> render ...
>
> The render call would be executed and if the user blocked the redirect
> he/she would be able to see the page.
>
> And validations should be in your model anyway. There is
> validates_confirmation_of for this password-confirmation ;-)
>
> --
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
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That''s what I was thinking...so why does rails give me the error
message? It
should not see the redirect_to below right?

-bakki

On 1/10/06, Kyle Maxwell <kyle@kylemaxwell.com>
wrote:
>
>
> Render doesn''t return, for reverse-compatibility reasons.
>
> --
> Kyle Maxwell
> Chief Technologist
> E Factor Media // FN Interactive
> kyle@efactormedia.com
> 1-866-263-3261
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>
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It could either be seeing the redirect OR the render. Either one will
give you the error message. The way you have it setup now is that if
the first render is seen in the unless you will ALWAYS see another
render (either redirect in the if, or the render with your else).
Throw a return statement after the unless render and you''ll be good to
go, or restructure it so its only got one exit point.

On 1/10/06, Bakki Kudva <bakki.kudva@gmail.com>
wrote:
> That''s what I was thinking...so why does rails give me the error
message? It
> should not see the redirect_to below right?
>
>  -bakki
>
>
> On 1/10/06, Kyle Maxwell <kyle@kylemaxwell.com> wrote:
> >
> > Render doesn''t return, for reverse-compatibility reasons.
> >
> > --
> > Kyle Maxwell
> > Chief Technologist
> > E Factor Media // FN Interactive
> > kyle@efactormedia.com
> > 1-866-263-3261
> >
> > _______________________________________________
> > Rails mailing list
> > Rails@lists.rubyonrails.org
> > http://lists.rubyonrails.org/mailman/listinfo/rails
> >
> >
> >
>
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>