From: Glen Holcomb <damnbigman@...>
Date: 2009-07-17T06:14:41+09:00
Subject: Re: uninitialized stream (IOError)

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Thanks Brian.

On Thu, Jul 16, 2009 at 1:19 PM, Brian Candler <b.candler@pobox.com> wrote:

> You're trying to mix subclassing and delegation.
>
> That is: your object is a subclass of File, and therefore an instance of
> ConfigStub *is* a File. However you are also opening another File and
> storing it in the instance variable @stub, and therefore it *has* a File
> as well.
>
> Choose one or the other. In my experience, delegation is the most
> flexible and understandable approach, and although it needs some setting
> up it ends up being simplest in the long run.
>
> You can delegate manually:
>
> class ConfigStub
>  def initialize(location)
>    @stub =3D File.open(...)
>  end
>  def each(*args,&blk)
>    @stub.each(*args,&blk)
>  end
>  def read(*args)
>    @stub.read(*args)
>  end
>  ... etc, and/or
>  def method_missing(*args,&blk)
>    @stub.__send__(*args,&blk)
>  end
> end
>
> or use a wrapped up version of this - check out SimpleDelegator in
> delegate.rb in the standard library.
>
> If you want to subclass File, then you'll need to ensure you call its
> initialize method. Probably something like this (untested):
>
> class ConfigStub < File
>  def initialize(location)
>     ..
>    super(CONFIG_PATH + filename, "w+")  # in the superclass
>  end
> end
>
> But subclassing core classes can get you tied up in knots if you're not
> careful (as I think you've already discovered)
>
> Regards,
>
> Brian.
> --
> Posted via http://www.ruby-forum.com/.
>
>


--=20
"Hey brother Christian with your high and mighty errand, Your actions speak
so loud, I can=92t hear a word you=92re saying."

-Greg Graffin (Bad Religion)

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