From: Florian Gross <flgr@...>
Date: 2004-08-29T10:20:32+09:00
Subject: Re: accessors break "no state change outside the object"?

zuzu wrote:

> ruby accessors are merely shortcuts for reading/writing @-scope values
> in an object.
> http://www.ruby-doc.org/docs/ruby-doc-bundle/UsersGuide/rg/accessors.html

As I understand it Ruby's accessors are just convenient ways of adding 
something to the interface of your Object that does modify state 
internally. (Without the interface part enforcing that.)

attr_accessor basically does this:

class Module
   def attr_accessor(name)
     define_method(name) do
       instance_variable_get(:"@#{name}")
     end
     define_method(:"#{name}=") do |value|
       instance_variable_set(:"@#{name}", value)
     end
   end
end

That is, attr_accessor :foo creates two methods foo() and foo=(). You 
can also create those manually and they need not be related to an 
instance variable at all so I don't think this breaks encapsulation.

> why create special syntax for initialization / object creation (.new)
> that also isn't specified with the .initialize / .new method?

I don't see how this is related, but .new / .initialize are *no* special 
syntax.

Class#new is defined like this:

class Class
   def new(*args, &block)
     result = self.allocate
     result.send(:initialize, *args, &block)
     return result
   end
end

Class#allocate is special of course, because it needs to construct an 
Object. You can't easily do that manually. (It's possible when using 
evil-ruby, but there's no real purpose in doing so.)

So basically I don't see where accessors or Class#new break Ruby's basic 
principles. I think Ruby is very consistent here. But then again I might 
just not be understanding your objections -- if so, please try to 
explain them in more detail.

> peace,
> -z

Regards,
Florian Gross