From: ara.t.howard@...
Date: 2006-06-30T23:45:08+09:00
Subject: Re: Useful inconcistency in calling foo vs. foo= private methods.

On Fri, 30 Jun 2006, Alder Green wrote:

> Hi
>
> This is an interesting sort of useful gotcha I recently stumbled upon:
>
> class Foo
> private
>
> def bar
>   p '#bar called'
> end
> def bar=(val)
>   p '#bar= called'
> end
> end
>
> irb(main):002:0> foo = Foo.new
> irb(main):003:0> foo.instance_eval { self.bar }
> NoMethodError: private method `bar' called for #<Foo:0x2c85a68>
> irb(main):004:0> foo.instance_eval { self.bar = 1 }
> "#bar= called"
>
> Formally, the the last line should have thrown an exception as well;
> afaik private methods can't by definition be called with an explicit
> receiver. It seems the assignment methods are exempt from this rule.
> This is actually useful, since it overrides the higher precendence of
> local variable assignment over method calls; if self.bar= didn't work,
> I don't see any way short of self.send to call the private #bar=.

a useful idiom

   class Foo
   private

     def bar *a
       if a.size == 0
         @bar
       else
         __send__ 'bar=', a.shift
       end
     end
     def bar= val
       @bar = val
     end
   end

   Foo.new.instance_eval{ bar 42 }

it avoids the issue somewhat.

regards.

-a
-- 
suffering increases your inner strength.  also, the wishing for suffering
makes the suffering disappear.
- h.h. the 14th dali lama