From: Joel VanderWerf <vjoel@...>
Date: 2006-05-25T13:01:35+09:00
Subject: Re: Marshaling NArray objects.

Alex Polite wrote:
> I'm trying to marshal narray objects by first converting them to
> ordinary arrays but I can't seem to get it right. I understand that I
> have to implement marshal_dump and marshal_load for NArray so I've
> tried this:
> 
> class NArray
>  def marshal_dump
>    self.to_a
>  end
> 
> def marshal_load(array)
>   NArray.to_narray(array)
> end
> end
> 
> And lots of other stuff. I won't bore you with the error messages,
> suffice to say that I can't seem to get it right.

One problem is that #marshal_load needs to populate self with the data,
rather than just instantiating a new object. In other words, don't
bother returning a new NArray from marshal_load--it won't be used.

Example:

class C
  attr_accessor :x, :y

  def marshal_dump
    [x, y]
  end

  def marshal_load(ary)
    p ary
    @x, @y = ary # <-- populate self with persisted data
  end
end

c = C.new
c.x = "foo"
c.y = "bar"

s = Marshal.dump(c)
p Marshal.load(s)

__END__

Output:

["foo", "bar"]
#<C:0xb7dbc220 @y="bar", @x="foo">


Is there a NArray method like Array#replace ? That would probably do the
trick, if you called it in marshal_load with the narray as its argument.

-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407