From: Kirk Haines <khaines@...>
Date: 2004-04-24T01:01:17+09:00
Subject: Re: attr_accessor vs. local variable

On Sat, 24 Apr 2004, Its Me wrote:

> Ruby not seem to predictably recognize attribute accessors (including
> setters) as such unless preceded by "self.attr".  But it recognizes other
> self messages fine. I suspect this has something to do with its rule on what
> is deemed a local variable.
> 
> What rule / ambiguity causes this?
> 
> class A
>   attr_accessor :x, :y
> 
>   def initialize
>     p x      # local or @x?
>     x=5      # does not call self.x=
>     self.y=5      # sets @y
>     foo          # calls self.foo
>   end
> 
>   def foo
>     p 'foo'
>   end
> 
> end
> 
> p A.new.x
> p A.new.y

This makes sense.  When you 'p x', all ruby knows about at that point is 
the accessor method.

So p x == p @x

When you get to x=5, though, Ruby says, "Ah!  A local variable" and 
assigns 5 to the local variable x.

See below:

enigodev src % irb
irb(main):001:0> def x
irb(main):002:1>  7
irb(main):003:1> end
=> nil
irb(main):004:0> puts x
7
=> nil
irb(main):005:0> x = 4
=> 4
irb(main):006:0> puts x
4


Kirk Haines