From: "Mauricio Fernández" <batsman.geo@...>
Date: 2004-08-26T07:34:14+09:00
Subject: Re: *with* block?

On Thu, Aug 26, 2004 at 06:56:13AM +0900, David A. Black wrote:
> > There is an awkward work around.  First write +with+ like this:
> > 
> >   module Kernel
> >     def with(obj, &block)
> >       obj.instance_eval { @self = eval("self", block) }
> >       obj.instance_eval &block
> >     end
> >   end
> > 
[...]
> You could also do:
> 
>   def testing_dog
>     s = self
>     t = Test.new
>     talk
>     with t do
>       test
>       s.talk
>     end
>   end
> 
> (i.e., put the burden of providing a reference to self-the-Dog to on
> the method, rather than on 'with')

It also has the additional benefit of being thread-safe, or more
precisely not as thread-unsafe :P
Also, polluting the original object with another i.v. feels very wrong.

You could also do

batsman@tux-chan:/tmp$ cat fdgdfg.rb
def with(obj, &block)
    o = Object.new
    s = self
    # I'd use define_method but {|*a,&b| ...} is 1.9 only
    o.instance_eval{ @self = s; @obj = obj }
    class << o
        def method_missing(meth,*a,&b)
            @obj.send(meth, *a, &b)
        end
    end
    o.instance_eval(&block)
end

class Foo
    def foo
        puts "Foo#foo"
        with(Bar.new){ bar; @self.babar{ puts "foo" } }
    end
    def babar
        puts "1931"
        yield
    end
end

class Bar; def bar; puts "Bar#bar" end end

Foo.new.foo


batsman@tux-chan:/tmp$ ruby fdgdfg.rb
Foo#foo
Bar#bar
1931
foo

But I don't really like it.

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