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candlerb

2009-Nov-19 22:39 UTC

Terminating a request early with throw or raise

Is there a standard way in Rails of terminating a request early with
throw or raise?

I am thinking of when a controller invokes a private method and inside
that method I wish to render a result and then finish. For example:

  def my_action
    ...
    authorize_something
    ...
  end

private
  def authorize_something
    ...
    if some_failure_condition
      flash[:error] = "I couldn''t do that"
      redirect_to :controller=>:top, :action=>:index
      throw :request_complete    # <<< WHAT GOES HERE?
    end
  end

that is, without having to put an explicit catch or rescue in every
action which calls authorize_something, and without having to check
the return value from authorize_something everywhere that it is
called.

I have found ''rescue_from''; however this doesn''t do
what I need
because my Cucumber tests still abort with the exception. That is, it
seems that rescue_from is intended to handle pretty display of error
pages when "real" exceptions occur, not as a mechanism by which a user
exception can signal the early (but successful) termination of a
request.

Is there any other facility I should be looking at?

Many thanks,

Brian.

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eugenio

2009-Nov-19 22:56 UTC

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Re: Terminating a request early with throw or raise

i don''t know if i understand what you need, but i usually put various
checks on a befor_filter. if conditions are not met you will simply
return false and the execution stops.

On 19 Nov, 23:39, candlerb
<b.cand...-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>
wrote:> Is there a standard way in Rails of terminating a request early with
> throw or raise?
>
> I am thinking of when a controller invokes a private method and inside
> that method I wish to render a result and then finish. For example:
>
>   def my_action
>     ...
>     authorize_something
>     ...
>   end
>
> private
>   def authorize_something
>     ...
>     if some_failure_condition
>       flash[:error] = "I couldn''t do that"
>       redirect_to :controller=>:top, :action=>:index
>       throw :request_complete    # <<< WHAT GOES HERE?
>     end
>   end
>
> that is, without having to put an explicit catch or rescue in every
> action which calls authorize_something, and without having to check
> the return value from authorize_something everywhere that it is
> called.
>
> I have found ''rescue_from''; however this doesn''t
do what I need
> because my Cucumber tests still abort with the exception. That is, it
> seems that rescue_from is intended to handle pretty display of error
> pages when "real" exceptions occur, not as a mechanism by which a
user
> exception can signal the early (but successful) termination of a
> request.
>
> Is there any other facility I should be looking at?
>
> Many thanks,
>
> Brian.
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Conrad Taylor

2009-Nov-19 23:45 UTC

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Re: Terminating a request early with throw or raise

On Thu, Nov 19, 2009 at 2:39 PM, candlerb
<b.candler-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org> wrote:
> Is there a standard way in Rails of terminating a request early with
> throw or raise?
>
>Why do you need to terminate a request early?  Is this an HTTP request?

-Conrad

> I am thinking of when a controller invokes a private method and inside
> that method I wish to render a result and then finish. For example:
>
>  def my_action
>    ...
>    authorize_something
>    ...
>  end
>
> private
>  def authorize_something
>    ...
>    if some_failure_condition
>      flash[:error] = "I couldn''t do that"
>      redirect_to :controller=>:top, :action=>:index
>      throw :request_complete    # <<< WHAT GOES HERE?
>    end
>  end
>
> that is, without having to put an explicit catch or rescue in every
> action which calls authorize_something, and without having to check
> the return value from authorize_something everywhere that it is
> called.
>
> I have found ''rescue_from''; however this doesn''t
do what I need
> because my Cucumber tests still abort with the exception. That is, it
> seems that rescue_from is intended to handle pretty display of error
> pages when "real" exceptions occur, not as a mechanism by which a
user
> exception can signal the early (but successful) termination of a
> request.
>
> Is there any other facility I should be looking at?
>
> Many thanks,
>
> Brian.
>
> --
>
> You received this message because you are subscribed to the Google Groups
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>
>
>
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candlerb

2009-Nov-20 07:27 UTC

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Re: Terminating a request early with throw or raise

> Why do you need to terminate a request early?  Is this an HTTP request?
By "request" I meant "controller action".

Within a method called by the controller action, I want to render
something and then prevent the controller action from continuing any
further (otherwise I''d get a double-render error, and/or the
controller would make changes to the database state which I don''t want
it to).

I am aware of before_filter. but in this case I will have gone quite a
long way into the controller action logic before it''s known that I
need to terminate this particular request. It doesn''t divide neatly
into "pre-condition check" and then "do stuff".

I thought I had seen somewhere that there was a way to terminate a
request early, but I could be thinking of a different framework. In
Sinatra you can ''throw :halt, response''.

Regards,

Brian.

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Jarkko Laine

2009-Nov-20 07:49 UTC

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Re: Terminating a request early with throw or raise

On Nov 19, 11:27 pm, candlerb
<b.cand...-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>
wrote:> > Why do you need to terminate a request early?  Is this an HTTP
request?
>
> By "request" I meant "controller action".
>
> Within a method called by the controller action, I want to render
> something and then prevent the controller action from continuing any
> further (otherwise I''d get a double-render error, and/or the
> controller would make changes to the database state which I don''t
want
> it to).
>
> I am aware of before_filter. but in this case I will have gone quite a
> long way into the controller action logic before it''s known that I
> need to terminate this particular request. It doesn''t divide
neatly
> into "pre-condition check" and then "do stuff".
>
> I thought I had seen somewhere that there was a way to terminate a
> request early, but I could be thinking of a different framework. In
> Sinatra you can ''throw :halt, response''.
Just return. Actions are normal Ruby methods. E.g:

return redirect_to(users_path)

//jarkko

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Frederick Cheung

2009-Nov-20 09:15 UTC

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Re: Terminating a request early with throw or raise

On Nov 20, 7:27 am, candlerb
<b.cand...-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>
wrote:> I thought I had seen somewhere that there was a way to terminate a
> request early, but I could be thinking of a different framework. In
> Sinatra you can ''throw :halt, response''.
If you do want those semantics (perhaps because you''re inside one or
more helper methods where it''s not so convenient to just render and
return) then it should be easy enough to recreate them with an around
filter.

Fred

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candlerb

2009-Nov-20 11:00 UTC

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Re: Terminating a request early with throw or raise

> If you do want those semantics (perhaps because you''re inside one
or
> more helper methods where it''s not so convenient to just render
and
> return) then it should be easy enough to recreate them with an around
> filter.
An around_filter with catch and yield would do the job. I hadn''t
thought of that, thanks.

Or I might just let the exception bubble upwards to rescue_from, and
test the exception rather than the display. e.g. in Cucumber,

Then /^it should be forbidden if (.*)$/ do |thing|
  assert_raises(Forbidden) { When thing }
end

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Rails - Nov 2009 - Terminating a request early with throw or raise

Terminating a request early with throw or raise

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