From: Florian Gross <flgr@...>
Date: 2004-11-15T22:18:20+09:00
Subject: Re: OpenStruct#update ?

Robert Klemme wrote:

> "Florian Gross" <flgr@ccan.de> schrieb im Newsbeitrag
>>h.each do |k,v|
>>   class << o; self; end.send(:attr_accessor, k)
>>   o.k = v
>>end
> 
> Are you sure, this works?  IMHO this is more efficient:
> 
> class << o; self; end.send(:attr_accessor, *h.keys)
> h.each do |k,v|
>    o.send("#{k}=", v)
> end

You are right of course. I also like how you moved the attr_accessor out 
of the loop -- nice idea.

> But it would be even better to check for existing methods in order to not
> overwrite existing methods:
> 
> cl = class << o; self; end
> im = cl.instance_methods
> h.each do |k,v|
>    cl.send(:attr_reader, k) unless im.include?(k.to_s)
>    cl.send(:attr_writer, k) unless im.include?("#{k}=")
>    o.send("#{k}=", v)
> end

Hm, I think that would still overwrite methods of o's class and 
inherited ones.

What about this?

accessors = h.keys - o.methods
class << o; self; end.send(:attr_accessor, *accessors)
h.each do |key, value|
   o.send("#{key}=", value) if accessors.include?(key)
end