From: Robert Klemme <bob.news@...>
Date: 2004-11-16T05:18:19+09:00
Subject: Re: OpenStruct#update ?


"Florian Gross" <flgr@ccan.de> schrieb im Newsbeitrag 
news:2vrtthF2n19d2U1@uni-berlin.de...
> Robert Klemme wrote:
>
>> The singleton class of f knows about instance methods defined in super
>> classes.  Which is logical, considering this:
>
> Ah, I was confusing instance_methods() with instance_methods(false).
>
>>>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
>>
>> Nice and short.  But it has some drawbacks:
>> [...]
>>
>> You would want ":bar" removed from the keys but it isn't because 
>> f.methods
>> returns an array of String.  (I assume that symbols are the most likely
>> keys for the hash - which might be wrong.)
>
> Hm, I assumed the hash would contain Strings as keys. I guess it could be 
> normalized to that.

I'd prefer symbols - partly because they are more memory efficient and 
partly because method id's are symbols, too.  (Yeah, I know that all 
#methods returns strings and send() et. al can deal with strings, too.   But 
I prefer to think of an identifier as a symbol rather as a string.)

>> Plus, it's not selective enough IMHO because if you just have a setter,
>> then that is overwritten.  And if you just have a getter, then no setter
>> is defined and you get an error during o.send("#{key}="...).
>
> I was trying to work around methods in Kernel -- I don't think it makes 
> sense to have o.p = when you don't have o.p.

Well, normall not.  But the other way round is more likely to occur, i.e., 
you don't have a setter but you have a getter.

> But I guess the check isn't strictly needed anyway. (attr_accessor :p will 
> create a public getter. I thought it would create a private one.)

Sorry, I'm not sure whether I understand what you mean here.  Could you 
please explain a bit more?

Kind regards

    robert