From: Sean O'Halpin <sean.ohalpin@...>
Date: 2006-07-26T18:15:40+09:00
Subject: Re: get caller of method

On 7/26/06, Ashley Moran <work@ashleymoran.me.uk> wrote:
> On Sunday 23 July 2006 22:55, Sean O'Halpin wrote:
> > Hi,
> >
> > It's not clear to me what you're doing with the binding. You don't
> > need it for your example and it won't work the way you seem to think.
> >
> > The example below shows you don't need to do anything fancy to get hold of
> > self:
> >
>
> < SNIP bit that shows me up as clueless :) >

Don't take it so hard - we're all still learning :)

>
> >
> > Please feel free to correct me if I've gotten hold of the wrong end of
> > the stick (it has been known ;)
> >
> > Regards,
> > Sean
>
>
> Hi Sean
>
> Seems I misunderstood the scope of "self".  I assumed that since a Food
> instance was calling a method in another object (the application instance of
> Object) that self would be the global "main" object.  IE:
>
> irb(main):003:0> class Foo
> irb(main):004:1>   def test
> irb(main):005:2>     global_test
> irb(main):006:2>   end
> irb(main):007:1> end
> => nil
> irb(main):008:0> def global_test
> irb(main):009:1>   puts self.class
> irb(main):010:1>   puts self.inspect
> irb(main):011:1> end
> => nil
> irb(main):012:0> Foo.new.test
>
> I expected:
> Object
> main
>
> But you actually get:
> Foo
> #<Foo:0x8143b18>
>
>
> I have to say, I don't understand this behaviour.  Maybe I am missing
> something.  I assume it is to do with class nesting?
>
> Ashley
>
self is dynamically scoped to always return the current receiver.

It is not lexically scoped, i.e. it does not depend on ~where~ the
definition is but on how it is called.

Look at this example:

@name = "I'm main"
def name
  @name
end

def m1
  p [self, name]
  @name = name.reverse
end

m1 # called in scope of self == main

class Foo
  attr_accessor :name
  def initialize(name)
    @name = name
  end
  def name
    @name
  end
  def m2
    m1 # called in scope of self == instance of Foo
  end
end

f = Foo.new("I'm foo")
f.m2
f.m2
__END__
[#<Object:0x27f91f8 @name="I'm main">, "I'm main"]
[#<Foo:0x2867598 @name="I'm foo">, "I'm foo"]
[#<Foo:0x2867598 @name="oof m'I">, "oof m'I"]

HTH

Regards,
Sean