From: Robert Klemme <shortcutter@...>
Date: 2012-10-26T16:41:04+09:00
Subject: Re: Name/symbol/object type clash? What is happening here?

On Thu, Oct 25, 2012 at 6:25 PM, Igor Pirnovar <lists@ruby-forum.com> wrote:
> Robert Klemme wrote in post #1081146:
>
>> I strongly object.  Struct is a very useful tool I use all the time to
>> define data containers quickly.
>
>>> The above problem can be solved if you use accessor methods in place of
>>> '@' variable:
>>
>> Exactly.
>
> I have no objection if anybody wishes to use the broken Struct as it is

It's not broken.  It works like designed.

> in his/her own short-cuts and sketches. However, if allowed there, who
> is going to prevent its use in main-stream programming?

Nobody, why should they?

> The trouble is,
> this stuff is so broken in situations becomes totally useless. Its
> inconsistencies with regular ruby classes make things unacceptable on
> the first place, and I can not believe anyone would defend its
> continuous usage in this broken fashion! If it is so bloody useful, fix
> the darn thing so it doesn't introduce unnecessary exceptions to the
> impeccable consistent and beautiful Ruby oo language!

You are repeating that it is broken but you fail to explain what
exactly is broken.  That's not a basis for discussions.

> Try to fix the following without redefining the redefining accessor for
> 'num' instance variable within the class definition hence invalidating
> the use of Struct:
>
>   S = Struct.new(:num)
>   class S
>     attr_accessor :num
>     def initialize(n); @num=n+5; end
>     def num=(n); @num = n+5; end
>   end
>
>   s = S.new(3)
>   puts s.num     #=> 8
>   s.num = 4
>   puts s.num     #=> 9

Easy:

S = Struct.new :num do
  alias _initialize initialize
  def initialize(n)
    super
    self.num = n
  end

  alias _num= num=
  def num=(n) self._num= n + 5 end
end

s = S.new 0
p s.num

Btw, having an accessor that changes the value in this way is probably
a questionable practice in itself.

Cheers

robert


-- 
remember.guy do |as, often| as.you_can - without end
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