From: Hugh Sasse Staff Elec Eng <hgs@...>
Date: 2000-03-17T14:51:22+00:00
Subject: [ruby-talk:01975] Re: Enumerations and all that.

On 17 Mar 2000, Dave Thomas wrote:

> Hugh Sasse Staff Elec Eng <hgs@dmu.ac.uk> writes:
> 
> > >      s = Spigot.new
> > > 
> > >      s.color = :red
> > >      s.size  = :large
> > > 
> > >      p s.color
> > >      p s.size
> > 
> > This can only be done for classes which have been given the enum method.
> > Also, this 'looks' like encapsulation is being broken, because s.color is
> > not a method call, but accessing something inside s.
> 
> That's in accordance with Meyer's uniform access principle, and a
> pretty common idiom. The important thing is that the implementation
> allows you to change the setter method transparently to the user. As
> these is never any direct access to instance variables, there's never
> any cases of broken encapsulation in Ruby when you see a.b = c (unless
> the class designer chose to break encapsulation, that is).

	:-) Ok, I stand corrected.
> 
> > > Anyway, here's all the code. It works under 1.5, but I'm not sure if
> > > the new Symbol stuff means it doesn't work under 1.4.
> > 
> > Not sure what you mean here, the only "unusual" thing is the id2name
> > but that is in the 1.4 manual.
> 
> In Ruby 1.5.3, :fred returns an object of class Symbol, not a Fixnum.
> 
	Oh, I see. 
> 
> 
> Regards
> 
> Dave
> 
	Thanks,
	Hugh
	hgs@dmu.ac.uk