From: Anton Aylward <anton@...>
Date: 2007-12-07T08:04:59+09:00
Subject: Re: Custom error handling question

Some enlightenment.

Firstly, the CustomError.new goes in the block of code that is yeilded
to, not in the wrapper.

Secondly, even though I've found examples in the ruby libraray and rails
of handlers beign extended  and having methods of their own, I cna;'t
get it o work.

For example, in actionpack/lib/action_view/base.rb
there is

   begin
        render_template(template_extension, template_source,
                        template_file_name, local_assigns)
      rescue Exception => e
        if TemplateError === e
          e.sub_template_of(template_file_name)
          ....

but when I try

	rescue CustomError => e
            puts "Caught #{e.message.to_s}"
            e.handle("#{e.message.to_s}",
                     "#{e.setup2.to_s}", "#{e.string3.to_s}")

the handle method doesn't get invoked.  I don't get an error message
about it either.

I have, of course

class CustomError < StandardError

  attr_accessor :setup1, :setup2, :setup3

  def initialize(setup1, setup2, setup3)
    @setup1 = setup1
    @setup2 = setup2
    @setup3 = setup3
    puts "Custom Error handler registered with #{@setup1.to_s},
                                               #{@setup2.to_s},
                                               #{setup3.to_s}"
  end

  def handle( handle1, handle2, handle3)
     puts "Custom error handler handled"
     puts "\tsetup1 = #{@setup1}"
     puts "\tsetup2 = #{@setup2}"
     puts "\tsetup3 = #{@setup3}"
     puts "\thandle1 = #{handle1}"
     puts "\thandle2 = #{handle2}"
     puts "\thandle3 = #{handle3}"
  end

end





Anton Aylward said the following on 06/12/07 01:58 PM:
> I'm trying to port something I've done in Perl to Ruby and am getting
> myself confused, or perhaps drowned in details between the various files.
> 
> I'm trying to write a custom error handler class.
> The documentation tells me that you can extend the Error class with a
> custom one that does more.
> 
> So I started with
> 
> class CustomError < StandardError
> 
>  def initialise(arg1, arg2, arg3, *args)
>    .....
>    .....
>  end
> 
>  def handle( opt1, opt2, opt3)
>    ....
>    ....
>  end
> end
> 
> I then had a wrapper that wrapped around the code that did the work.
> 
>   def dothefanango(context, &codeblock)
>     oops = CustomError.new( context, stuff, more_stuff)
>     begin
>         yield context
>     rescue CustomError ...
>            oops.handle(......)
>            ....
>     rescue CustomError other than the one above
>            .......
>     rescue StandardError ....
>            ....
>     else
>            ....
>   end
> 
> In principle, all well and good.  In practice the details are killing me.
> 
> The pickaxe book says that the rescue clause can have parameters, but
> I'm also concerned with the 'raise' passing back information - more than
> just a string.
> 
> I'm drowning in the details and don't know what to try and experiment
> with. Any advice would be appreciated.


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