From: Brian Candler <b.candler@...>
Date: 2009-07-17T04:19:14+09:00
Subject: Re: uninitialized stream (IOError)

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 = 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.
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